Saturate alpha values when overlaying glyphs
Saturate alpha values when overlaying glyphs

bug:19062769

Glyphs were stored to the output buffer with the assumption of
non-overlap, which is incorrect for certain fonts/strings. Instead,
blend src into dst, so new glyphs don't clobber existing content.

Change-Id: I6e22037500e67d5348ee2a43d939416c23c4d1ea

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base