Update from https://crrev.com/308331

cc/test/test_context_provider.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/test/test_context_provider.h"
 
 #include <set>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/logging.h"
 #include "cc/test/test_gles2_interface.h"
 #include "cc/test/test_web_graphics_context_3d.h"
+#include "third_party/skia/include/gpu/GrContext.h"
+#include "third_party/skia/include/gpu/gl/GrGLInterface.h"
 
 namespace cc {
 
 // static
 scoped_refptr<TestContextProvider> TestContextProvider::Create() {
   return Create(TestWebGraphicsContext3D::Create().Pass());
 }
 
 // static
 scoped_refptr<TestContextProvider> TestContextProvider::Create(
@@ skipping 58 matching lines @@
 }
 
 gpu::ContextSupport* TestContextProvider::ContextSupport() {
   return &support_;
 }
 
 class GrContext* TestContextProvider::GrContext() {
   DCHECK(bound_);
   DCHECK(context_thread_checker_.CalledOnValidThread());
 
-  // TODO(danakj): Make a test GrContext that works with a test Context3d.
-  return NULL;
+  if (gr_context_)
+    return gr_context_.get();
+
+  auto null_interface = skia::AdoptRef(GrGLCreateNullInterface());
+  gr_context_ = skia::AdoptRef(GrContext::Create(
+      kOpenGL_GrBackend,
+      reinterpret_cast<GrBackendContext>(null_interface.get())));
+  return gr_context_.get();
 }
 
 bool TestContextProvider::IsContextLost() {
   DCHECK(bound_);
   DCHECK(context_thread_checker_.CalledOnValidThread());
 
   return context3d_->isContextLost();
 }
 
 void TestContextProvider::VerifyContexts() {
@@ skipping 59 matching lines @@
   DCHECK(memory_policy_changed_callback_.is_null() || cb.is_null());
   memory_policy_changed_callback_ = cb;
 }
 
 void TestContextProvider::SetMaxTransferBufferUsageBytes(
     size_t max_transfer_buffer_usage_bytes) {
   context3d_->SetMaxTransferBufferUsageBytes(max_transfer_buffer_usage_bytes);
 }
 
 }  // namespace cc