cc: Add null checks for GrContext created by ContextProviderCommandBuffer.

GrContext::Create may return NULL if the base GL context was lost.

 - Check for the NULL case in GlRenderer.
 - For the GPU rasterizer, don't allow GPU rasterization to be initialized
   with a NULL GrContext.

BUG=464892

Review URL: https://codereview.chromium.org/1135743004

Cr-Commit-Position: refs/heads/master@{#330104}

5 files changed, 39 insertions, 6 deletions

diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index bdb537a..93a4114 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -163,7 +163,13 @@ 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() {
diff --git a/cc/test/fake_output_surface.h b/cc/test/fake_output_surface.h
index 6028cad..7041a44 100644
--- a/cc/test/fake_output_surface.h
+++ b/cc/test/fake_output_surface.h
@@ -29,7 +29,8 @@ class FakeOutputSurface : public OutputSurface {
 
   static scoped_ptr<FakeOutputSurface> Create3d(
       scoped_refptr<ContextProvider> context_provider) {
-    return make_scoped_ptr(new FakeOutputSurface(context_provider, false));
+    return make_scoped_ptr(new FakeOutputSurface(
+        context_provider, TestContextProvider::Create(), false));
   }
 
   static scoped_ptr<FakeOutputSurface> Create3d(
@@ -41,8 +42,9 @@ class FakeOutputSurface : public OutputSurface {
 
   static scoped_ptr<FakeOutputSurface> Create3d(
       scoped_ptr<TestWebGraphicsContext3D> context) {
-    return make_scoped_ptr(new FakeOutputSurface(
-        TestContextProvider::Create(context.Pass()), false));
+    return make_scoped_ptr(
+        new FakeOutputSurface(TestContextProvider::Create(context.Pass()),
+                              TestContextProvider::Create(), false));
   }
 
   static scoped_ptr<FakeOutputSurface> CreateSoftware(
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 6125337..4df3807 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1584,6 +1584,20 @@ void LayerTreeHostImpl::FinishAllRendering() {
     renderer_->Finish();
 }
 
+bool LayerTreeHostImpl::CanUseGpuRasterization() {
+  if (!(output_surface_ && output_surface_->context_provider() &&
+        output_surface_->worker_context_provider()))
+    return false;
+
+  ContextProvider* context_provider =
+      output_surface_->worker_context_provider();
+  base::AutoLock context_lock(*context_provider->GetLock());
+  if (!context_provider->GrContext())
+    return false;
+
+  return true;
+}
+
 void LayerTreeHostImpl::UpdateGpuRasterizationStatus() {
   bool use_gpu = false;
   bool use_msaa = false;
@@ -1613,6 +1627,17 @@ void LayerTreeHostImpl::UpdateGpuRasterizationStatus() {
     gpu_rasterization_status_ = GpuRasterizationStatus::OFF_CONTENT;
   }
 
+  if (use_gpu && !use_gpu_rasterization_) {
+    if (!CanUseGpuRasterization()) {
+      // If GPU rasterization is unusable, e.g. if GlContext could not
+      // be created due to losing the GL context, force use of software
+      // raster.
+      use_gpu = false;
+      use_msaa = false;
+      gpu_rasterization_status_ = GpuRasterizationStatus::OFF_DEVICE;
+    }
+  }
+
   if (use_gpu == use_gpu_rasterization_ && use_msaa == use_msaa_)
     return;
 
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 54776e7..7e01faf 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -327,6 +327,7 @@ class CC_EXPORT LayerTreeHostImpl
   void set_content_is_suitable_for_gpu_rasterization(bool flag) {
     content_is_suitable_for_gpu_rasterization_ = flag;
   }
+  bool CanUseGpuRasterization();
   void UpdateGpuRasterizationStatus();
   bool use_gpu_rasterization() const { return use_gpu_rasterization_; }
   bool use_msaa() const { return use_msaa_; }
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index cc239da..9476645 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -5931,8 +5931,7 @@ TEST_F(LayerTreeHostImplTest, MemoryPolicy) {
   // when visible.
   LayerTreeSettings settings;
   settings.gpu_rasterization_enabled = true;
-  host_impl_ = LayerTreeHostImpl::Create(
-      settings, this, &proxy_, &stats_instrumentation_, NULL, NULL, NULL, 0);
+  CreateHostImpl(settings, CreateOutputSurface());
   host_impl_->set_content_is_suitable_for_gpu_rasterization(true);
   host_impl_->set_has_gpu_rasterization_trigger(true);
   host_impl_->UpdateGpuRasterizationStatus();