Require sRGB write control for sRGB support. Add flag to GrPaint to suppress linear -> sRGB convers…

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index bcb3c193dc6a5b537546ef40e6edf97a44e55dfc..61fdb8fa33677b22e27279cd4b112c6a9c09d956 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -328,7 +328,7 @@ private:
 
     // bounds is region that may be modified.
     // nullptr means whole target. Can be an empty rect.
-    void flushRenderTarget(GrGLRenderTarget*, const SkIRect* bounds);
+    void flushRenderTarget(GrGLRenderTarget*, const SkIRect* bounds, bool disableSRGB = false);
     // Handles cases where a surface will be updated without a call to flushRenderTarget
     void didWriteToSurface(GrSurface*, const SkIRect* bounds) const;