Revert of PageAnimator: estimate number of documents and reserveIniti…

…alCapacity (patchset nwjs#1 id:1 of https://codereview.chromium.org/883573003/)

Reason for revert:
Appears to be causing crashes in browser tests due to bad LocalFrame casts: http://build.chromium.org/p/chromium.webkit/builders/Linux%20Tests%20(dbg)/builds/5376/steps/content_browsertests/logs/KillingRendererClearsDescendantProxies

Original issue's description:
> PageAnimator: estimate number of documents and reserveInitialCapacity
> 
> PageAnimator::serviceScriptedAnimation is called every frame.
> The vector expansion should be kept minimal for performance.
> 
> The CL adds reserveInitialCapacity to avoid dynamic expand.
> 
> BUG=452351
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=189003

TBR=dstockwell@chromium.org,haraken@chromium.org,kouhei@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=452351

Review URL: https://codereview.chromium.org/880053002

git-svn-id: svn://svn.chromium.org/blink/trunk@189051 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Source/core/page/PageAnimator.cpp

@@ -41,8 +41,6 @@ void PageAnimator::serviceScriptedAnimations(double monotonicAnimationStartTime)
     TemporaryChange<bool> servicing(m_servicingAnimations, true);
 
     WillBeHeapVector<RefPtrWillBeMember<Document>> documents;
-    ASSERT(m_page->mainFrame());
-    documents.reserveInitialCapacity(m_page->mainFrame()->tree().scopedChildCount());
     for (Frame* frame = m_page->mainFrame(); frame; frame = frame->tree().traverseNext()) {
         if (frame->isLocalFrame())
             documents.append(toLocalFrame(frame)->document());