Improve array checking for Serializable/Clonable. Check if something is array over class instance is costly and direct check is simple to implement. Change-Id: Iaeb32125ded3cde99a6f53bc40cc65d3ce41b838

diff --git a/user/super/com/google/gwt/emul/java/io/Serializable.java b/user/super/com/google/gwt/emul/java/io/Serializable.java
index 3032baf..9458df5 100644
--- a/user/super/com/google/gwt/emul/java/io/Serializable.java
+++ b/user/super/com/google/gwt/emul/java/io/Serializable.java

@@ -16,6 +16,7 @@
 package java.io;
 
 import javaemul.internal.JsUtils;
+import javaemul.internal.NativeArray;
 import jsinterop.annotations.JsMethod;
 
 /**
@@ -37,7 +38,7 @@
         || type.equals("string")
         || instance.getTypeMarker()
         // Arrays are implicitly instances of Serializable (JLS 10.7).
-        || instance.getClass().isArray();
+        || NativeArray.isArray(instance);
   }
   // CHECKSTYLE_ON: end utility methods
 }

diff --git a/user/super/com/google/gwt/emul/java/lang/Cloneable.java b/user/super/com/google/gwt/emul/java/lang/Cloneable.java
index 74535b4..907f569 100644
--- a/user/super/com/google/gwt/emul/java/lang/Cloneable.java
+++ b/user/super/com/google/gwt/emul/java/lang/Cloneable.java

@@ -15,6 +15,7 @@
  */
 package java.lang;
 
+import javaemul.internal.NativeArray;
 import jsinterop.annotations.JsMethod;
 
 /**
@@ -31,7 +32,7 @@
 
     return instance.getTypeMarker()
         // Arrays are implicitly instances of Cloneable (JLS 10.7).
-        || instance.getClass().isArray();
+        || NativeArray.isArray(instance);
   }
   // CHECKSTYLE_ON: end utility methods
 }

diff --git a/user/super/com/google/gwt/emul/javaemul/internal/NativeArray.java b/user/super/com/google/gwt/emul/javaemul/internal/NativeArray.java
index 7f0ea99..792ab3c 100644
--- a/user/super/com/google/gwt/emul/javaemul/internal/NativeArray.java
+++ b/user/super/com/google/gwt/emul/javaemul/internal/NativeArray.java

@@ -39,4 +39,6 @@
   public native Object[] slice(int fromIndex, int toIndex);
   public native void splice(int index, int deleteCount, @DoNotAutobox Object... value);
   public native <T> void sort(CompareFunction compareFunction);
+
+  public static native boolean isArray(Object o);
 }