Due to Adreno bug in glReadPixels

BUG=angleproject:1413
TEST=ReadPixelsTest.OutOfBounds

Change-Id: I2fd426bc6d21f5d9604ca32ad34dd8841cbb9a3e
Reviewed-on: https://chromium-review.googlesource.com/353363Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>