Merge 139017. Requested by yusufo@google.com

Merge 139017. Requested by yusufo@google.com
> Don't use double tap zoom if minimum and maximum page scale is the same
> https://bugs.webkit.org/show_bug.cgi?id=106272
> 
> Patch by Yusuf Ozuysal <yusufo@google.com>; on 2013-01-07
> Reviewed by James Robinson.
> 
> We should only try to computed relevant scale and scrollOffset and start the animation
> if the page is zoomable. This now creates an undesired animation for mobile pages which
> are not zoomable.
> 
> * src/WebViewImpl.cpp:
> (WebKit::WebViewImpl::handleGestureEvent):

TBR=commit-queue@webkit.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=139115