SF: Skip render-to-texture for color transforms

In cases where SurfaceFlinger is applying a color matrix (usually for
accessibility features), we previously would perform a render-to-
texture for the initial composition, and then apply the matrix during
a copy to the framebuffer. This changes that behavior to just apply the
matrix during composition without a render-to-texture pass.

This may result in a perceived change of the image in cases with alpha
blending, since the blending is performed at a different stage of the
pipeline and the system effectively performs non-linear blends.
However, neither this nor the prior render-to-texture pass is strictly
correct in that regard, and this approach is less error-prone and
likely faster.

Change-Id: I2110ff0374f61d76df7b087dde8a1ed98990440c
diff --git a/services/surfaceflinger/RenderEngine/GLES20RenderEngine.h b/services/surfaceflinger/RenderEngine/GLES20RenderEngine.h
index 3d6243e..819356a 100644
--- a/services/surfaceflinger/RenderEngine/GLES20RenderEngine.h
+++ b/services/surfaceflinger/RenderEngine/GLES20RenderEngine.h
@@ -72,14 +72,12 @@
     virtual void setupLayerTexturing(const Texture& texture);
     virtual void setupLayerBlackedOut();
     virtual void setupFillWithColor(float r, float g, float b, float a);
+    virtual mat4 setupColorTransform(const mat4& colorTransform);
     virtual void disableTexturing();
     virtual void disableBlending();
 
     virtual void drawMesh(const Mesh& mesh);
 
-    virtual void beginGroup(const mat4& colorTransform);
-    virtual void endGroup();
-
     virtual size_t getMaxTextureSize() const;
     virtual size_t getMaxViewportDims() const;
 };