diff --git a/dev/core/src/com/google/gwt/dev/jjs/LibraryJavaToJavaScriptCompiler.java b/dev/core/src/com/google/gwt/dev/jjs/LibraryJavaToJavaScriptCompiler.java
index 25f560b..561f759 100644
--- a/dev/core/src/com/google/gwt/dev/jjs/LibraryJavaToJavaScriptCompiler.java
+++ b/dev/core/src/com/google/gwt/dev/jjs/LibraryJavaToJavaScriptCompiler.java
@@ -277,7 +277,7 @@
         String resourcePath = entry.getKey();
         File resourceFile = entry.getValue();
         compilerContext.getLibraryWriter()
-            .addBuildResource(FileResource.create(null, resourcePath, resourceFile));
+            .addBuildResource(FileResource.of(resourcePath, resourceFile));
       }
     }
 
diff --git a/dev/core/src/com/google/gwt/dev/resource/impl/AbstractResource.java b/dev/core/src/com/google/gwt/dev/resource/impl/AbstractResource.java
index f0f9308..fe6a1e8 100644
--- a/dev/core/src/com/google/gwt/dev/resource/impl/AbstractResource.java
+++ b/dev/core/src/com/google/gwt/dev/resource/impl/AbstractResource.java
@@ -22,11 +22,6 @@
  */
 public abstract class AbstractResource extends Resource {
 
-  /**
-   * Accesses the path root under which this resource was found. Only available within this package.
-   */
-  public abstract ClassPathEntry getClassPathEntry();
-
   @Override
   public boolean wasRerooted() {
     return false;
diff --git a/dev/core/src/com/google/gwt/dev/resource/impl/ClassPathEntry.java b/dev/core/src/com/google/gwt/dev/resource/impl/ClassPathEntry.java
index c7655e9..83edd86 100644
--- a/dev/core/src/com/google/gwt/dev/resource/impl/ClassPathEntry.java
+++ b/dev/core/src/com/google/gwt/dev/resource/impl/ClassPathEntry.java
@@ -17,8 +17,6 @@
 
 import com.google.gwt.core.ext.TreeLogger;
 
-import java.util.ArrayList;
-import java.util.List;
 import java.util.Map;
 
 /**
@@ -41,22 +39,6 @@
   }
 
   /**
-   * Finds applicable resources for a list of pathPrefixSets, returning a
-   * distinct answer for each set.
-   *
-   * @see #findApplicableResources(TreeLogger, PathPrefixSet)
-   */
-  public List<Map<AbstractResource, ResourceResolution>> findApplicableResources(
-      TreeLogger logger, List<PathPrefixSet> pathPrefixSets) {
-    List<Map<AbstractResource, ResourceResolution>> results = new ArrayList<
-        Map<AbstractResource, ResourceResolution>>(pathPrefixSets.size());
-    for (PathPrefixSet pathPrefixSet : pathPrefixSets) {
-      results.add(findApplicableResources(logger, pathPrefixSet));
-    }
-    return results;
-  }
-
-  /**
    * Finds every resource at abstract path P within this classpath such that P
    * begins with a prefix X from the path prefix set and P is allowed by the
    * filter associated with X.
diff --git a/dev/core/src/com/google/gwt/dev/resource/impl/DirectoryClassPathEntry.java b/dev/core/src/com/google/gwt/dev/resource/impl/DirectoryClassPathEntry.java
index 1bc2a34..e496f21 100644
--- a/dev/core/src/com/google/gwt/dev/resource/impl/DirectoryClassPathEntry.java
+++ b/dev/core/src/com/google/gwt/dev/resource/impl/DirectoryClassPathEntry.java
@@ -24,7 +24,6 @@
 
 import java.io.File;
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.IdentityHashMap;
 import java.util.List;
@@ -81,18 +80,6 @@
   }
 
   @Override
-  public List<Map<AbstractResource, ResourceResolution>> findApplicableResources(
-      TreeLogger logger, List<PathPrefixSet> pathPrefixSets) {
-    List<Map<AbstractResource, ResourceResolution>> results =
-        new ArrayList<Map<AbstractResource, ResourceResolution>>(pathPrefixSets.size());
-    for (PathPrefixSet pathPrefixSet : pathPrefixSets) {
-      results.add(new IdentityHashMap<AbstractResource, ResourceResolution>());
-    }
-    descendToFindResources(logger, pathPrefixSets, results, dir, "");
-    return results;
-  }
-
-  @Override
   public Map<AbstractResource, ResourceResolution> findApplicableResources(TreeLogger logger,
       PathPrefixSet pathPrefixSet) {
     if (!WATCH_FILE_CHANGES) {
@@ -150,7 +137,7 @@
         DirectoryPathPrefixChangeManager.getAndClearChangedFiles(this, pathPrefixSet);
     for (File changedFile : changedFiles) {
       String changedRelativePath = Util.makeRelativePath(dir, changedFile);
-      FileResource resource = FileResource.create(this, changedRelativePath, changedFile);
+      FileResource resource = FileResource.of(changedRelativePath, changedFile);
 
       if (!changedFile.exists()) {
         if (resolutionsByResource.containsKey(resource)) {
@@ -229,7 +216,7 @@
           ResourceResolution resourceResolution = null;
           if ((resourceResolution = pathPrefixSets.get(i).includesResource(childPath)) != null) {
             Messages.INCLUDING_FILE.log(logger, childPath, null);
-            FileResource r = FileResource.create(this, childPath, child);
+            FileResource r = FileResource.of(childPath, child);
             results.get(i).put(r, resourceResolution);
           } else {
             Messages.EXCLUDING_FILE.log(logger, childPath, null);
diff --git a/dev/core/src/com/google/gwt/dev/resource/impl/FileResource.java b/dev/core/src/com/google/gwt/dev/resource/impl/FileResource.java
index 9ca55b3..46174e3 100644
--- a/dev/core/src/com/google/gwt/dev/resource/impl/FileResource.java
+++ b/dev/core/src/com/google/gwt/dev/resource/impl/FileResource.java
@@ -15,58 +15,44 @@
  */
 package com.google.gwt.dev.resource.impl;
 
-import com.google.gwt.thirdparty.guava.common.collect.Maps;
+import com.google.gwt.thirdparty.guava.common.collect.MapMaker;
 
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.lang.ref.WeakReference;
-import java.util.Map;
+import java.util.concurrent.ConcurrentMap;
 
 /**
  * Represents a resource contained in a directory on a file system.
- * <p>
- * The class is immutable and automatically interned.
+ * <p>The class is immutable and automatically interned.
  */
 public class FileResource extends AbstractResource {
+  /*
+   * The #equals and #hashCode is locked to work on identities by the base class Resource.
+   * Without interning, it would be impractical to use this class as a key in a map.
+   */
 
-  private static Map<String, FileResource> fileResourceByKey = Maps.newHashMap();
+  private static final ConcurrentMap<String, FileResource> canonicalFileResources =
+      new MapMaker().weakValues().makeMap();
 
-  public static FileResource create(DirectoryClassPathEntry classPathEntry, String abstractPathName,
-      File file) {
-    // Intern the file resource.
-    String classPathLocation = classPathEntry != null ? classPathEntry.getLocation() : "null";
-    String key = classPathLocation + File.pathSeparator + abstractPathName + File.pathSeparator
-        + file.getAbsolutePath();
-    FileResource fileResource = fileResourceByKey.get(key);
-    if (fileResource == null) {
-      fileResource = new FileResource(classPathEntry, abstractPathName, file);
-      fileResourceByKey.put(key, fileResource);
-    }
-
-    return fileResource;
+  public static FileResource of(String abstractPathName, File file) {
+    String key = abstractPathName + "@" + file.getAbsolutePath();
+    FileResource sample = new FileResource(abstractPathName, file);
+    FileResource canonical = canonicalFileResources.putIfAbsent(key, sample);
+    return (canonical == null) ? sample : canonical;
   }
 
   private final String abstractPathName;
-  private final WeakReference<DirectoryClassPathEntry> classPathEntryReference;
   private final File file;
 
-  private FileResource(DirectoryClassPathEntry classPathEntry, String abstractPathName, File file) {
+  private FileResource(String abstractPathName, File file) {
     assert (file.isFile()) : file + " is not a file.";
-    this.classPathEntryReference = new WeakReference<DirectoryClassPathEntry>(classPathEntry);
     this.abstractPathName = abstractPathName;
     this.file = file;
   }
 
   @Override
-  public DirectoryClassPathEntry getClassPathEntry() {
-    DirectoryClassPathEntry classPathEntry = classPathEntryReference.get();
-    assert classPathEntry != null;
-    return classPathEntry;
-  }
-
-  @Override
   public long getLastModified() {
     return file.lastModified();
   }
diff --git a/dev/core/src/com/google/gwt/dev/resource/impl/ResourceOracleImpl.java b/dev/core/src/com/google/gwt/dev/resource/impl/ResourceOracleImpl.java
index 6b0f5d2..3cd1026 100644
--- a/dev/core/src/com/google/gwt/dev/resource/impl/ResourceOracleImpl.java
+++ b/dev/core/src/com/google/gwt/dev/resource/impl/ResourceOracleImpl.java
@@ -78,11 +78,6 @@
     }
 
     @Override
-    public ClassPathEntry getClassPathEntry() {
-      return resource.getClassPathEntry();
-    }
-
-    @Override
     public long getLastModified() {
       return resource.getLastModified();
     }
diff --git a/dev/core/src/com/google/gwt/dev/resource/impl/UrlResource.java b/dev/core/src/com/google/gwt/dev/resource/impl/UrlResource.java
index d4608e5..7dd5642 100644
--- a/dev/core/src/com/google/gwt/dev/resource/impl/UrlResource.java
+++ b/dev/core/src/com/google/gwt/dev/resource/impl/UrlResource.java
@@ -36,11 +36,6 @@
   }
 
   @Override
-  public ClassPathEntry getClassPathEntry() {
-    throw new UnsupportedOperationException("UrlResources do not come from the class path.");
-  }
-
-  @Override
   public long getLastModified() {
     return lastModified;
   }
diff --git a/dev/core/src/com/google/gwt/dev/resource/impl/ZipFileResource.java b/dev/core/src/com/google/gwt/dev/resource/impl/ZipFileResource.java
index f96186a..07ea34b 100644
--- a/dev/core/src/com/google/gwt/dev/resource/impl/ZipFileResource.java
+++ b/dev/core/src/com/google/gwt/dev/resource/impl/ZipFileResource.java
@@ -63,11 +63,6 @@
   }
 
   @Override
-  public ZipFileClassPathEntry getClassPathEntry() {
-    return classPathEntry;
-  }
-
-  @Override
   public long getLastModified() {
     return lastModified;
   }
diff --git a/dev/core/test/com/google/gwt/dev/resource/impl/FileResourceTest.java b/dev/core/test/com/google/gwt/dev/resource/impl/FileResourceTest.java
index 4a48426..f74b744 100644
--- a/dev/core/test/com/google/gwt/dev/resource/impl/FileResourceTest.java
+++ b/dev/core/test/com/google/gwt/dev/resource/impl/FileResourceTest.java
@@ -21,7 +21,6 @@
 
 import java.io.File;
 import java.io.IOException;
-import java.io.InputStream;
 
 /**
  * Tests related FileResources.
@@ -29,19 +28,9 @@
 public class FileResourceTest extends TestCase {
 
   public void testBasic() {
-    File f = null;
-    try {
-      f = File.createTempFile("com.google.gwt.dev.javac.impl.FileResourceTest",
-          ".tmp");
-      f.deleteOnExit();
-      Util.writeStringAsFile(f, "contents 1");
-    } catch (IOException e) {
-      fail("Failed to create test file");
-    }
+    File f = createTempFile();
 
-    File dir = f.getParentFile();
-    DirectoryClassPathEntry cpe = new DirectoryClassPathEntry(dir);
-    FileResource r = FileResource.create(cpe, f.getName(), f);
+    FileResource r = FileResource.of(f.getName(), f);
     assertEquals(f.getAbsoluteFile().toURI().toString(), r.getLocation());
 
     /*
@@ -52,19 +41,9 @@
   }
 
   public void testDeletion() {
-    File f = null;
-    try {
-      f = File.createTempFile("com.google.gwt.dev.javac.impl.FileResourceTest",
-          ".tmp");
-      f.deleteOnExit();
-      Util.writeStringAsFile(f, "contents 1");
-    } catch (IOException e) {
-      fail("Failed to create test file");
-    }
+    File f = createTempFile();
 
-    File dir = f.getParentFile();
-    DirectoryClassPathEntry cpe = new DirectoryClassPathEntry(dir);
-    FileResource r = FileResource.create(cpe, f.getName(), f);
+    FileResource r = FileResource.of(f.getName(), f);
     assertEquals(f.getAbsoluteFile().toURI().toString(), r.getLocation());
 
     /*
@@ -80,11 +59,31 @@
      *  The resource is no longer available.  Check to make sure we can't access its contents
      *  through the API.
      */
-    InputStream in = null;
     try {
-      in = r.openContents();
+      r.openContents();
       fail("Open contents unexpectedly succeeded.");
     } catch (IOException expected) {
     }
   }
+
+  public void testInterning() throws Exception {
+    File f = createTempFile();
+
+    assertSame(FileResource.of(f.getName(), f), FileResource.of(f.getName(), f));
+    // A different FileResourse will return even files match if the pathname is different.
+    assertNotSame(FileResource.of(f.getName(), f), FileResource.of(f.getName() + "x", f));
+  }
+
+  private File createTempFile() {
+    File f = null;
+    try {
+      f = File.createTempFile("com.google.gwt.dev.javac.impl.FileResourceTest", ".tmp");
+      f.deleteOnExit();
+      Util.writeStringAsFile(f, "contents 1");
+    } catch (IOException e) {
+      fail("Failed to create test file");
+    }
+    return f;
+  }
+
 }
diff --git a/dev/core/test/com/google/gwt/dev/resource/impl/MockAbstractResource.java b/dev/core/test/com/google/gwt/dev/resource/impl/MockAbstractResource.java
index 6c8c756..fbe9235 100644
--- a/dev/core/test/com/google/gwt/dev/resource/impl/MockAbstractResource.java
+++ b/dev/core/test/com/google/gwt/dev/resource/impl/MockAbstractResource.java
@@ -33,11 +33,6 @@
   }
 
   @Override
-  public ClassPathEntry getClassPathEntry() {
-    return mockClassPathEntry;
-  }
-
-  @Override
   public long getLastModified() {
     return 0;
   }
diff --git a/dev/core/test/com/google/gwt/dev/resource/impl/ResourceOracleImplTest.java b/dev/core/test/com/google/gwt/dev/resource/impl/ResourceOracleImplTest.java
index 0691588..c19ea92 100644
--- a/dev/core/test/com/google/gwt/dev/resource/impl/ResourceOracleImplTest.java
+++ b/dev/core/test/com/google/gwt/dev/resource/impl/ResourceOracleImplTest.java
@@ -111,8 +111,11 @@
     public void assertPathIncluded(String expectedPath, ClassPathEntry expectedCpe) {
       AbstractResource resource = findResourceWithPath(expectedPath);
       assertNotNull(resource);
-      ClassPathEntry actualCpe = resource.getClassPathEntry();
-      assertEquals(expectedCpe.getLocation(), actualCpe.getLocation());
+      if (expectedCpe.getLocation().endsWith(".jar")) {
+        assertTrue(resource.getLocation().startsWith("jar:" + expectedCpe.getLocation()));
+      } else {
+        assertTrue(resource.getLocation().startsWith(expectedCpe.getLocation()));
+      }
     }
 
     public void assertPathNotIncluded(String path) {