Perf experiment (to be reverted): use system malloc on Mac.

BUG=310744
R=abarth@chromium.org
TBR=abarth@chromium.org

Review URL: https://codereview.chromium.org/35423009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230577 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230577
cc: Fix touch hit-testing for overlapping layers (in tests).

If a touch-layer is below a non-touch layer, and the two layers overlap,
then the overlapped region should not be treated as a touch-handling region.
This change updates FindLayerThatIsHitByPointInTouchHandlerRegion() to do the
right thing (which is currently used only in tests), and uses this function from
LayerTreeHostImpl::HaveTouchEventHandlersAt() (instead of having its own code).

BUG=none
R=enne@chromium.org

Review URL: https://codereview.chromium.org/27718006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230578 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230578