Add a makeDrawContextWithFallback that handles config fallback

src/gpu/GrTextureParamsAdjuster.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 "GrTextureParamsAdjuster.h"
 
 #include "GrCaps.h"
@@ skipping 15 matching lines @@
 
 typedef GrTextureProducer::CopyParams CopyParams;
 
 //////////////////////////////////////////////////////////////////////////////
 
 static GrTexture* copy_on_gpu(GrTexture* inputTexture, const SkIRect* subset,
                               const CopyParams& copyParams) {
     SkASSERT(!subset || !subset->isEmpty());
     GrContext* context = inputTexture->getContext();
     SkASSERT(context);
-    const GrCaps* caps = context->caps();
 
     GrPixelConfig config = GrMakePixelConfigUncompressed(inputTexture->config());
 
-    // If the config isn't renderable try converting to either A8 or an 32 bit config. Otherwise,
-    // fail.
-    if (!caps->isConfigRenderable(config, false)) {
-        if (GrPixelConfigIsAlphaOnly(config)) {
-            if (caps->isConfigRenderable(kAlpha_8_GrPixelConfig, false)) {
-                config = kAlpha_8_GrPixelConfig;
-            } else if (caps->isConfigRenderable(kSkia8888_GrPixelConfig, false)) {
-                config = kSkia8888_GrPixelConfig;
-            } else {
-                return nullptr;
-            }
-        } else if (kRGB_GrColorComponentFlags ==
-                (kRGB_GrColorComponentFlags & GrPixelConfigComponentMask(config))) {
-            if (caps->isConfigRenderable(kSkia8888_GrPixelConfig, false)) {
-                config = kSkia8888_GrPixelConfig;
-            } else {
-                return nullptr;
-            }
-        } else {
-            return nullptr;
-        }
-    }
-
     sk_sp<GrDrawContext> copyDC = context->makeDrawContext(SkBackingFit::kExact, copyParams.fWidth,
                                                            copyParams.fHeight, config, nullptr);
     if (!copyDC) {
         return nullptr;
     }
 
     GrPaint paint;
     paint.setGammaCorrect(true);
 
     SkScalar sx SK_INIT_TO_AVOID_WARNING;
@@ skipping 462 matching lines @@
 }
 
 GrTexture* GrTextureMaker::generateTextureForParams(const CopyParams& copyParams, bool willBeMipped,
                                                     SkSourceGammaTreatment gammaTreatment) {
     SkAutoTUnref<GrTexture> original(this->refOriginalTexture(willBeMipped, gammaTreatment));
     if (!original) {
         return nullptr;
     }
     return copy_on_gpu(original, nullptr, copyParams);
 }