cc: Add null checks for GrContext created by ContextProviderCommandBuffer.

cc/output/gl_renderer.cc

 // Copyright 2010 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/output/gl_renderer.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 #include <string>
@@ skipping 145 matching lines @@
 static GLint GetActiveTextureUnit(GLES2Interface* gl) {
   GLint active_unit = 0;
   gl->GetIntegerv(GL_ACTIVE_TEXTURE, &active_unit);
   return active_unit;
 }
 
 class GLRenderer::ScopedUseGrContext {
  public:
   static scoped_ptr<ScopedUseGrContext> Create(GLRenderer* renderer,
                                                DrawingFrame* frame) {
-    return make_scoped_ptr(new ScopedUseGrContext(renderer, frame));
+    // GrContext for filters is created lazily, and may fail if the context
+    // is lost.
+    // TODO(vmiura,bsalomon): crbug.com/487850 Ensure that
+    // ContextProvider::GrContext() does not return NULL.
+    if (renderer->output_surface_->context_provider()->GrContext())
+      return make_scoped_ptr(new ScopedUseGrContext(renderer, frame));
+    return nullptr;
   }
 
   ~ScopedUseGrContext() {
     // Pass context control back to GLrenderer.
     scoped_gpu_raster_ = nullptr;
     renderer_->RestoreGLState();
     renderer_->RestoreFramebuffer(frame_);
   }
 
   GrContext* context() const {
@@ skipping 3324 matching lines @@
     context_support_->ScheduleOverlayPlane(
         overlay.plane_z_order,
         overlay.transform,
         pending_overlay_resources_.back()->texture_id(),
         ToNearestRect(overlay.display_rect),
         overlay.uv_rect);
   }
 }
 
 }  // namespace cc