Re-enable ForceReclaimResources w/ ui impl side painting

Disabling ForceReclaimResource on BeginCommit when using ui impl side painting
had the unintended consequence of breaking Display::Draw's mechanism for
not drawing while an OutputSurface was between Commit/Swap. Re enabling
this for now. Tracking handling this in a more robust way in
crbug.com/489515.

BUG=481656,489515

Review URL: https://codereview.chromium.org/1139823008

Cr-Commit-Position: refs/heads/master@{#330587}

cc/trees/layer_tree_host_impl.cc

@@ -297,9 +297,12 @@ void LayerTreeHostImpl::BeginCommit() {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::BeginCommit");
 
   // Ensure all textures are returned so partial texture updates can happen
-  // during the commit. Impl-side-painting doesn't upload during commits, so
-  // is unaffected.
-  if (!settings_.impl_side_painting && output_surface_)
+  // during the commit.
+  // TODO(ericrk): We should not need to ForceReclaimResources when using
+  // Impl-side-painting as it doesn't upload during commits. However,
+  // Display::Draw currently relies on resource being reclaimed to block drawing
+  // between BeginCommit / Swap. See crbug.com/489515.
+  if (output_surface_)
     output_surface_->ForceReclaimResources();
 
   if (settings_.impl_side_painting && !proxy_->CommitToActiveTree())

cc/trees/layer_tree_host_impl_unittest.cc

@@ -7774,5 +7774,40 @@ TEST_F(LayerTreeHostImplTest, GpuRasterizationStatusModes) {
   EXPECT_TRUE(host_impl_->use_gpu_rasterization());
 }
 
+// A mock output surface which lets us detect calls to ForceReclaimResources.
+class MockReclaimResourcesOutputSurface : public FakeOutputSurface {
+ public:
+  static scoped_ptr<MockReclaimResourcesOutputSurface> Create3d() {
+    return make_scoped_ptr(new MockReclaimResourcesOutputSurface(
+        TestContextProvider::Create(), TestContextProvider::Create(), false));
+  }
+
+  MOCK_METHOD0(ForceReclaimResources, void());
+
+ protected:
+  MockReclaimResourcesOutputSurface(
+      scoped_refptr<ContextProvider> context_provider,
+      scoped_refptr<ContextProvider> worker_context_provider,
+      bool delegated_rendering)
+      : FakeOutputSurface(context_provider,
+                          worker_context_provider,
+                          delegated_rendering) {}
+};
+
+// Display::Draw (and the planned Display Scheduler) currently rely on resources
+// being reclaimed to block drawing between BeginCommit / Swap. This test
+// ensures that BeginCommit triggers ForceReclaimResources. See
+// crbug.com/489515.
+TEST_F(LayerTreeHostImplTest, BeginCommitReclaimsResources) {
+  scoped_ptr<MockReclaimResourcesOutputSurface> output_surface(
+      MockReclaimResourcesOutputSurface::Create3d());
+  // Hold an unowned pointer to the output surface to use for mock expectations.
+  MockReclaimResourcesOutputSurface* mock_output_surface = output_surface.get();
+
+  CreateHostImpl(DefaultSettings(), output_surface.Pass());
+  EXPECT_CALL(*mock_output_surface, ForceReclaimResources()).Times(1);
+  host_impl_->BeginCommit();
+}
+
 }  // namespace
 }  // namespace cc