Defer starting of animations until after compositing update

Source/core/page/PageAnimator.cpp

 // 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 "config.h"
 #include "core/page/PageAnimator.h"
 
 #include "core/animation/DocumentAnimations.h"
 #include "core/dom/Document.h"
 #include "core/frame/Frame.h"
 #include "core/frame/FrameView.h"
 #include "core/page/Page.h"
 
 namespace WebCore {
 
 PageAnimator::PageAnimator(Page* page)
     : m_page(page)
     , m_servicingAnimations(false)
 {
 }
 
 void PageAnimator::serviceScriptedAnimations(double monotonicAnimationStartTime)
 {
     TemporaryChange<bool> servicing(m_servicingAnimations, true);
 
     for (RefPtr<Frame> frame = m_page->mainFrame(); frame; frame = frame->tree().traverseNext()) {
         frame->view()->serviceScrollAnimations();
-        DocumentAnimations::serviceOnAnimationFrame(*frame->document(), monotonicAnimationStartTime);
+        DocumentAnimations::updateAnimationTimingForAnimationFrame(*frame->document(), monotonicAnimationStartTime);
+        DocumentAnimations::dispatchAnimationEvents(*frame->document());

[abarth-chromium, 2014/02/24 06:14:08]

Given that this function is dispatching events, don't we need to collect up the
RefPtr<Frame>s in a vector before walking them?  Scripts running below this call
stack can alter the frame tree, which can screw up the traversal.  (Feel free to
address this issue in a followup CL.)

[dstockwell, 2014/02/24 06:58:07]

Will do. Looks like we can use the same collection as below.

     }
 
     Vector<RefPtr<Document> > documents;
     for (Frame* frame = m_page->mainFrame(); frame; frame = frame->tree().traverseNext())
         documents.append(frame->document());

[abarth-chromium, 2014/02/24 06:14:08]

Notice that we collect up the documents here before calling
requestAnimationFrame callbacks for that very reason.

 
     for (size_t i = 0; i < documents.size(); ++i)
         documents[i]->serviceScriptedAnimations(monotonicAnimationStartTime);
 }
 
 }