Merge "libgui: Copyback all region except dirty region for newly allocated buffer"

        if (canCopyBack) {

            Mutex::Autolock lock(mMutex);

            Region oldDirtyRegion;

            if(mSlots[backBufferSlot].dirtyRegion.isEmpty()) {

                oldDirtyRegion.set(bounds);

            } else {

                for(int i = 0 ; i < NUM_BUFFER_SLOTS; i++ ) {

                    if(i != backBufferSlot && !mSlots[i].dirtyRegion.isEmpty())

                        oldDirtyRegion.orSelf(mSlots[i].dirtyRegion);

                }

            }

            const Region copyback(oldDirtyRegion.subtract(newDirtyRegion));

            if (!copyback.isEmpty())

                copyBlt(backBuffer, frontBuffer, copyback);