Surface: fix copy back dirty region

Copyback dirty region logic does copyback,
even when its not necessary causing 2ms delay.
Fix the logic to copy back only what is necessary.

(cherry picked from commit 9dc653a0fe16e70469a1a55f55da1a47c30d4d95)

Change-Id: I52de68258ac9f87d704ee5401f93417805fa6773
Merge "Surface: fix copy back dirty region" into android-4.4
merge changes from Omni 4.4 into local branch