cc: Fix race in ThreadProxy unittests.

This fixes the data race in ThreadProxyTestCommitWaitsForActivation.
Reported by TSAN.

BUG=437454
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1486253002

Cr-Commit-Position: refs/heads/master@{#369940}

cc/test/layer_tree_test.cc

@@ -653,6 +653,13 @@ void LayerTreeTest::PostCompositeImmediatelyToMainThread() {
                  main_thread_weak_ptr_));
 }
 
+void LayerTreeTest::PostNextCommitWaitsForActivationToMainThread() {
+  main_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&LayerTreeTest::DispatchNextCommitWaitsForActivation,
+                 main_thread_weak_ptr_));
+}
+
 void LayerTreeTest::WillBeginTest() {
   layer_tree_host_->SetVisible(true);
 }
@@ -800,6 +807,12 @@ void LayerTreeTest::DispatchCompositeImmediately() {
     layer_tree_host_->Composite(base::TimeTicks::Now());
 }
 
+void LayerTreeTest::DispatchNextCommitWaitsForActivation() {
+  DCHECK(!task_runner_provider() || task_runner_provider()->IsMainThread());
+  if (layer_tree_host_)
+    layer_tree_host_->SetNextCommitWaitsForActivation();
+}
+
 void LayerTreeTest::RunTest(CompositorMode mode, bool delegating_renderer) {
   mode_ = mode;
   if (mode_ == CompositorMode::Threaded) {

cc/test/layer_tree_test.h

@@ -90,6 +90,7 @@ class LayerTreeTest : public testing::Test, public TestHooks {
   void PostSetVisibleToMainThread(bool visible);
   void PostSetNextCommitForcesRedrawToMainThread();
   void PostCompositeImmediatelyToMainThread();
+  void PostNextCommitWaitsForActivationToMainThread();
 
   void DoBeginTest();
   void Timeout();
@@ -123,6 +124,7 @@ class LayerTreeTest : public testing::Test, public TestHooks {
   void DispatchSetNextCommitForcesRedraw();
   void DispatchDidAddAnimation();
   void DispatchCompositeImmediately();
+  void DispatchNextCommitWaitsForActivation();
 
   virtual void AfterTest() = 0;
   virtual void WillBeginTest();

cc/trees/layer_tree_host_unittest_proxy.cc

@@ -293,46 +293,46 @@ class ProxyMainThreadedCommitWaitsForActivation : public ProxyMainThreaded {
         // completion event is cleared.
         EXPECT_FALSE(GetProxyImplForTest()->HasCommitCompletionEvent());
         EXPECT_FALSE(GetProxyImplForTest()->GetNextCommitWaitsForActivation());
+
+        // Set next commit waits for activation and start another commit.
+        commits_completed_++;
+        PostNextCommitWaitsForActivationToMainThread();
+        PostSetNeedsCommitToMainThread();
         break;
       case 1:
         // The second commit should be held until activation.
         EXPECT_TRUE(GetProxyImplForTest()->HasCommitCompletionEvent());
         EXPECT_TRUE(GetProxyImplForTest()->GetNextCommitWaitsForActivation());
+
+        // Start another commit to verify that this is not held until
+        // activation.
+        commits_completed_++;
+        PostSetNeedsCommitToMainThread();
         break;
       case 2:
         // The third commit should not wait for activation.
         EXPECT_FALSE(GetProxyImplForTest()->HasCommitCompletionEvent());
         EXPECT_FALSE(GetProxyImplForTest()->GetNextCommitWaitsForActivation());
+
+        commits_completed_++;
     }
   }
 
   void DidActivateSyncTree() override {
     // The next_commit_waits_for_activation should have been cleared after the
     // sync tree is activated.
     EXPECT_FALSE(GetProxyImplForTest()->GetNextCommitWaitsForActivation());
+    if (commits_completed_ == 3)
+      EndTest();
   }
 
-  void DidCommit() override {
-    switch (commits_completed_) {
-      case 0:
-        // The first commit has been completed. Set next commit waits for
-        // activation and start another commit.
-        commits_completed_++;
-        proxy()->SetNextCommitWaitsForActivation();
-        proxy()->SetNeedsCommit();
-      case 1:
-        // Start another commit to verify that this is not held until
-        // activation.
-        commits_completed_++;
-        proxy()->SetNeedsCommit();
-      case 2:
-        commits_completed_++;
-        EndTest();
-    }
+  void AfterTest() override {
+    // It is safe to read commits_completed_ on the main thread now since
+    // AfterTest() runs after the LayerTreeHost is destroyed and the impl thread
+    // tear down is finished.
+    EXPECT_EQ(3, commits_completed_);
   }
 
-  void AfterTest() override { EXPECT_EQ(3, commits_completed_); }
-
  private:
   int commits_completed_;