sRGB support in Ganesh. Several pieces:

tests/SRGBReadWritePixelsTest.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Test.h"
 #if SK_SUPPORT_GPU
 #include "GrCaps.h"
@@ skipping 141 matching lines @@
         for (int i = 0; i < kW; ++i) {
             origData[j * kW + i] = (j << 24) | (i << 16) | (i << 8) | i;
         }
     }
 
     GrSurfaceDesc desc;
     desc.fFlags = kRenderTarget_GrSurfaceFlag;
     desc.fWidth = kW;
     desc.fHeight = kH;
     desc.fConfig = kSRGBA_8888_GrPixelConfig;
-    if (context->caps()->isConfigRenderable(desc.fConfig, false) &&
+    if (context->caps()->srgbSupport() &&
+        context->caps()->isConfigRenderable(desc.fConfig, false) &&
         context->caps()->isConfigTexturable(desc.fConfig)) {
         SkAutoTUnref<GrTexture> tex(context->textureProvider()->createTexture(
                 desc, SkBudgeted::kNo));
         if (!tex) {
             ERRORF(reporter, "Could not create SRGBA texture.");
             return;
         }
 
         float error = context->caps()->shaderCaps()->floatPrecisionVaries() ? 1.2f  : 0.5f;
 
@@ skipping 50 matching lines @@
         if (tex->writePixels(0, 0, kW, kH, kRGBA_8888_GrPixelConfig, origData)) {
             read_and_check_pixels(reporter, tex, origData, kSRGBA_8888_GrPixelConfig,
                                   check_linear_to_srgb_conversion, 1.2f,
                                   "write rgba/read srgba to rgba texture");
         } else {
             ERRORF(reporter, "Could not write rgba data to rgba texture.");
         }
     }
 }
 #endif