Add test_runner hook to dump drag image.

content/shell/renderer/test_runner/test_runner.h

Index: content/shell/renderer/test_runner/test_runner.h
diff --git a/content/shell/renderer/test_runner/test_runner.h b/content/shell/renderer/test_runner/test_runner.h
index ffb6bf0a4ee71e5a43902d4e33ef24e55cabc0da..24c66db7daf4faee5d5421f4679bd42848c36e63 100644
--- a/content/shell/renderer/test_runner/test_runner.h
+++ b/content/shell/renderer/test_runner/test_runner.h
@@ -119,6 +119,7 @@ class TestRunner : public WebTestRunner,
   void RequestPointerUnlock();
   bool isPointerLocked();
   void setToolTipText(const blink::WebString&);
+  bool shouldDumpDragImage();
 
   bool midiAccessorResult();
 
@@ -469,6 +470,10 @@ class TestRunner : public WebTestRunner,
   // WebFrameClient receives a loadURLExternally() call.
   void WaitUntilExternalURLLoad();
 
+  // This function sets a flag which tells the test_shell to dump the drag image
+  // when a drag-and-drop is initiated.
+  void DumpDragImage();
+
   ///////////////////////////////////////////////////////////////////////////
   // Methods interacting with the WebTestProxy
 
@@ -739,6 +744,9 @@ class TestRunner : public WebTestRunner,
   // taking possible transforms of the selection rect into account.
   bool dump_selection_rect_;
 
+  // If true, the test_shell will output a base64 encoded bitmap.
+  bool dump_drag_image_;
+
   // If true, pixel dump will be produced as a series of 1px-tall, view-wide
   // individual paints over the height of the view.
   bool test_repaint_;