Make Android WebView filtering depend on scrolling status.

This patch makes bilinear filtering of software images enabled only when
there is no scrolling or CSS animation active, which matches the
policy of classic WebView.  In the long run, we'll likely want to support
software tiling to avoid this kind of hack, but for now this maintains
bugwards compatibility.

Most of this patch is to solve the problem that CC was not aware whether
or not WebView-handled fling is active.  I added a new getter 
ScrollOffsetDelegate::IsExternalFlingActive for this.  This also
enables prefer-smoothness mode for these flings.

New test RendererPixelTest.PictureDrawQuadDisableImageFiltering

NOTRY=true
BUG= internal b/10706494

Review URL: https://codereview.chromium.org/25233002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227629 0039d316-1c4b-4281-b951-d872f2087c98
Fixed bug in Windows version detection causing test expectations to fail to apply.

BUG=225939
R=dtu@chromium.org

Review URL: https://codereview.chromium.org/26616003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227630 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227630