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..0a6e704b3d5c9e00265434f3f20006eb6ea32fab 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 +470,12 @@ class TestRunner : public WebTestRunner,
   // WebFrameClient receives a loadURLExternally() call.
   void WaitUntilExternalURLLoad();
 
+  // This function sets a flag which tells the WebTestProxy to dump the drag
+  // image when the next drag-and-drop is initiated. It is equivalent to
+  // DumpAsTextWithPixelResults but the pixel results will be the drag image
+  // instead of a snapshot of the page.
+  void DumpDragImage();
+
   ///////////////////////////////////////////////////////////////////////////
   // Methods interacting with the WebTestProxy
 
@@ -739,6 +746,9 @@ class TestRunner : public WebTestRunner,
   // taking possible transforms of the selection rect into account.
   bool dump_selection_rect_;
 
+  // If true, the test_shell will dump the drag image as pixel results.
+  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_;