Fix a possible starvation issue related to vsync.
Fix a possible starvation issue related to vsync.

This makes a noticeable improvement in cases where applications
post messages that need to be processed between animation frames.

Bug: 6418353
Change-Id: If225742e37aeaf3f0ca9710f9bf43dbb03bcde12

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