Tile priority in Android WebView

Cherry pick of chromium r286731


Original Description:
Tiling priorities in Android Webview.

Use the parent compositor's clip and transform for tile
priorities in child compositor.

When the transform matrix changes in parent compositor
(hardware_renderer.cc), it posts the matrix and the clip to
the child compositor. (The parent clip is in screen space
and the parent matrix transforms from webview space to
screen space) Child compositor will use them for tile

In child compositor during updating tile priority, the clip
from parent is transformed from screen space to view space,
then from view space to content space. Then the result rect
will intersect with content_bounds() and the intersection
is used as tile priority input.

Change-Id: I3d1625f46649f032215810729d24717e5faceff7
44 files changed