[US250] Fix screenshot functionality used by the "recent apps" widget.

Patch from:
https://gist.github.com/steven676/7276913/raw/9736b0962964a46ed7816fa622492d75cb868e17/0002-Restore-support-for-glReadPixels-screenshot-path.patch

From 1e81c876af6e11790632c9fdfd32768f970ccebe Mon Sep 17 00:00:00 2001
From: Steven Luo <steven+android@steven676.net>
Date: Fri, 1 Nov 2013 23:26:39 -0700
Subject: [PATCH 2/2] Restore support for glReadPixels screenshot path

This is needed for SGX530/540 GPUs.

This reverts commit 3ca76f416bc8665a97636ca8a2d0128b9da9d92c.

Conflicts:
	services/surfaceflinger/SurfaceFlinger.cpp

Change-Id: I52b29dac9bfe23d1f27bd2fe94db6b9adbcfd900
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