Make installLocationIframe.js in GWT compatible with CSP. This change removes "javascript:" assignment to src attribute of a newly created an iframe. This is effectively a no-op but creates a CSP violation. Manually tested on IE8, 9, 10, 11 and Edge, and current Firefox and Chrome. Change-Id: I4d5a1e66efadabba102703e7ce90c01b06a9c45b Review-Link: https://gwt-review.googlesource.com/#/c/18480/

diff --git a/dev/core/src/com/google/gwt/core/ext/linker/impl/installLocationIframe.js b/dev/core/src/com/google/gwt/core/ext/linker/impl/installLocationIframe.js
index fa9abad..59fca5c 100644
--- a/dev/core/src/com/google/gwt/core/ext/linker/impl/installLocationIframe.js
+++ b/dev/core/src/com/google/gwt/core/ext/linker/impl/installLocationIframe.js

@@ -31,22 +31,21 @@
   // Create the script frame, making sure it's invisible, but not
   // "display:none", which keeps some browsers from running code in it.
   var scriptFrame = $doc.createElement('iframe');
-  scriptFrame.src = 'javascript:""';
   scriptFrame.id = '__MODULE_NAME__';
   scriptFrame.style.cssText = 'position:absolute; width:0; height:0; border:none; left: -1000px;'
     + ' top: -1000px;';
   scriptFrame.tabIndex = -1;
   $doc.body.appendChild(scriptFrame);
 
-  frameDoc = scriptFrame.contentDocument;
-  if (!frameDoc) {
-    frameDoc = scriptFrame.contentWindow.document;
-  }
+  frameDoc = scriptFrame.contentWindow.document;
 
-  // The missing content has been seen on Safari 3 and firebug will
-  // behave incorrectly on soft refresh unless we explicitly set the content
-  // of the frame. However, we don't want to do this when runAsync calls
-  // installCode, so we do it here when we create the iframe.
+  // The following code is needed for proper operation in Firefox, Safari, and
+  // Internet Explorer.
+  //
+  // In Firefox, this prevents the frame from re-loading asynchronously and
+  // throwing away the current document.
+  //
+  // In IE, it ensures that the <body> element is immediately available.
   frameDoc.open();
   var doctype = (document.compatMode == 'CSS1Compat') ? '<!doctype html>' : '';
   frameDoc.write(doctype + '<html><head></head><body></body></html>');