For main thread event handling, if event causes
SetNeedsCommit, SetNeedsUpdateLayer or SetNeedsAnimate during
event processing, then it is considered to cause rendering and
its LatencyInfo is pushed into LayerTreeHost through
LatencyInfoSwapPromise.
    
For impl thread event handling, if event causes
SetNeedsRedraw or SetNeedsRedrawRect during event processing,
then it is considered to cause rendering and its LatencyInfo is
pushed into LayerTreeHostImpl through LatencyInfoSwapPromise.
    
BUG=246034, 271583
TEST=Manually tested on Pixel. The LatencyInfo for events that
causes impl/main thread scrolling are correctly passed to LTH/LTHI.

Review URL: https://codereview.chromium.org/55273003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239375 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239375