libgui : Fix copyback dirty region

This is a combination of 2 commits.

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

CRs-fixed: 562334
Change-Id: I52de68258ac9f87d704ee5401f93417805fa6773

libgui: Copyback all region except dirty region

Inside Surface::lock if new buffer is allocated
and DirtyRegion does not cover complete buffer
bounds then copyback may not cover all remaining area
as it copyback only area covered by dirty regions
from other buffers. This will lead to left out
black area which may cause flicker.

Change-Id: I4a3f7a56fc5fbaf4af926584919577d8d34bed57

Change-Id: I4a3f7a56fc5fbaf4af926584919577d8d34bed5f