ClipArea's region mode implementation store the region's boundary in
a rectangle, and if the region is that rectangle, set its region to
empty. This is a bug, since as long as the ClipArea is in region
mode it treats its region as determinitive. When the next clipping
operation comes in, it is tested against the empty region instead of
against the valid rect.
Discovered via Skia GM testing.
Change-Id: I3bbc4e81c8d68636061f830156e017e9b5c7e587
Create a ClipArea class to handle tracking clip regions. This class can
select the most efficient implementation depending on the types of
clipping presented.
ClipArea re-used the rectangle and region-based clipping
implementations as well as adding a "list of rotated rectangles"
approach that is more efficient for rotated views with children.
Change-Id: I2133761a2462ebc0852b394220e265974b3086f0
