Add test_runner hook to dump drag image.

content/shell/renderer/test_runner/web_test_proxy.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/shell/renderer/test_runner/web_test_proxy.h"
 
 #include <cctype>
 
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
@@ skipping 547 matching lines @@
   canvas.drawBitmap(bitmap, popup_position_.x(), popup_position_.y());
   callback_.Run(main_bitmap_);
   delete this;
 }
 
 void WebTestProxyBase::CapturePixelsAsync(
     const base::Callback<void(const SkBitmap&)>& callback) {
   TRACE_EVENT0("shell", "WebTestProxyBase::CapturePixelsAsync");
   DCHECK(!callback.is_null());
 
+  if (!drag_image_.isNull()) {

[Justin Novosad, 2015/02/13 03:00:05]

Theory on why this this CL introduced flake: drag_image_ is never reset, so it
may contain remnants of a previous test. I don't know this class very well but I
am guessing WebTestProxyBase::Reset() might be the right place. 

Also, I think you should be checking the test runner flag here to avoid falling
back to the regular pixel dump in the case where dumpDragImage was called but no
drag ever happened.  That would be an error in the test, and it should produce
an error in the test result (blank output?)

[jackhou1, 2015/02/13 04:54:44]

Yeah that does fix the flakiness: https://codereview.chromium.org/918313003/
That CL was failing on the CQ for some reason though.
I'll put together a new CL with that fix included.
Ah, good point, I'll make this change in the new CL.

+    callback.Run(drag_image_.getSkBitmap());
+    return;
+  }
+
   if (test_interfaces_->GetTestRunner()->isPrinting()) {
     base::MessageLoopProxy::current()->PostTask(
         FROM_HERE,
         base::Bind(&WebTestProxyBase::CapturePixelsForPrinting,
                    base::Unretained(this),
                    callback));
     return;
   }
 
   CaptureCallback* capture_callback = new CaptureCallback(base::Bind(
@@ skipping 221 matching lines @@
 
     delegate_->PrintMessage(message + "\n");
   }
 }
 
 void WebTestProxyBase::StartDragging(blink::WebLocalFrame* frame,
                                      const blink::WebDragData& data,
                                      blink::WebDragOperationsMask mask,
                                      const blink::WebImage& image,
                                      const blink::WebPoint& point) {
+  if (test_interfaces_->GetTestRunner()->shouldDumpDragImage()) {
+    if (drag_image_.isNull())
+      drag_image_ = image;
+  }
   // When running a test, we need to fake a drag drop operation otherwise
   // Windows waits for real mouse events to know when the drag is over.
   test_interfaces_->GetEventSender()->DoDragDrop(data, mask);
 }
 
 // The output from these methods in layout test mode should match that
 // expected by the layout tests. See EditingDelegate.m in DumpRenderTree.
 
 void WebTestProxyBase::DidChangeSelection(bool is_empty_callback) {
   if (test_interfaces_->GetTestRunner()->shouldDumpEditingCallbacks())
@@ skipping 494 matching lines @@
   // to cancel the input method's ongoing composition session.
   if (web_widget_)
     web_widget_->confirmComposition();
 }
 
 blink::WebString WebTestProxyBase::acceptLanguages() {
   return blink::WebString::fromUTF8(accept_languages_);
 }
 
 }  // namespace content