Fix DelegatedFrameResourceCollection thread safety

cc/layers/delegated_frame_resource_collection_unittest.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 "base/bind.h"
+#include "base/run_loop.h"
+#include "base/synchronization/waitable_event.h"
+#include "base/threading/thread.h"
+#include "cc/layers/delegated_frame_resource_collection.h"
+#include "cc/resources/returned_resource.h"
+#include "cc/resources/transferable_resource.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cc {
+namespace {
+
+class DelegatedFrameResourceCollectionTest
+    : public testing::Test,
+      public DelegatedFrameResourceCollectionClient {
+ protected:
+  DelegatedFrameResourceCollectionTest() : resources_available_(false) {}
+
+  virtual void SetUp() OVERRIDE { CreateResourceCollection(); }
+
+  virtual void TearDown() OVERRIDE { DestroyResourceCollection(); }
+
+  void CreateResourceCollection() {
+    DCHECK(!resource_collection_);
+    resource_collection_ = new DelegatedFrameResourceCollection;
+    resource_collection_->SetClient(this);
+  }
+
+  void DestroyResourceCollection() {
+    if (resource_collection_) {
+      resource_collection_->SetClient(NULL);
+      resource_collection_ = NULL;
+    }
+  }
+
+  TransferableResourceArray CreateResourceArray() {
+    TransferableResourceArray resources;
+    TransferableResource resource;
+    resource.id = 444;
+    resources.push_back(resource);
+    return resources;
+  }
+
+  virtual void UnusedResourcesAreAvailable() OVERRIDE {
+    resources_available_ = true;
+    resource_collection_->TakeUnusedResourcesForChildCompositor(
+        &returned_resources_);
+    if (!resources_available_closure_.is_null())
+      resources_available_closure_.Run();
+  }
+
+  bool ReturnAndResetResourcesAvailable() {
+    bool r = resources_available_;
+    resources_available_ = false;
+    return r;
+  }
+
+  scoped_refptr<DelegatedFrameResourceCollection> resource_collection_;
+  bool resources_available_;
+  ReturnedResourceArray returned_resources_;
+  base::Closure resources_available_closure_;
+};
+
+// This checks that taking the return callback doesn't take extra refcounts,
+// since it's sent to other threads.
+TEST_F(DelegatedFrameResourceCollectionTest, NoRef) {
+  // Start with one ref.
+  EXPECT_TRUE(resource_collection_->HasOneRef());
+
+  ReturnCallback return_callback =
+      resource_collection_->GetReturnResourcesCallbackForImplThread();
+
+  // Callback shouldn't take a ref since it's sent to other threads.
+  EXPECT_TRUE(resource_collection_->HasOneRef());
+}
+
+void ReturnResourcesOnThread(ReturnCallback callback,
+                             const ReturnedResourceArray& resources,
+                             base::WaitableEvent* event) {
+  callback.Run(resources);
+  event->Wait();
+}
+
+// Tests that the ReturnCallback can run safely on threads even after the
+// last references to the collection were dropped.
+TEST_F(DelegatedFrameResourceCollectionTest, Thread) {
+  base::Thread thread("test thread");
+  thread.Start();
+
+  TransferableResourceArray resources = CreateResourceArray();
+  resource_collection_->ReceivedResources(resources);
+  resource_collection_->RefResources(resources);
+
+  ReturnedResourceArray returned_resources;
+  TransferableResource::ReturnResources(resources, &returned_resources);
+
+  base::WaitableEvent event(false, false);
+
+  {
+    base::RunLoop run_loop;
+    resources_available_closure_ = run_loop.QuitClosure();
+
+    thread.message_loop()->PostTask(
+        FROM_HERE,
+        base::Bind(
+            &ReturnResourcesOnThread,
+            resource_collection_->GetReturnResourcesCallbackForImplThread(),
+            returned_resources,
+            &event));
+
+    run_loop.Run();
+  }
+  EXPECT_TRUE(ReturnAndResetResourcesAvailable());
+  EXPECT_EQ(1u, returned_resources_.size());
+  EXPECT_EQ(444u, returned_resources_[0].id);
+  EXPECT_EQ(1, returned_resources_[0].count);
+  returned_resources_.clear();
+
+  // The event prevents the return resources callback from being deleted.
+  // Destroy the last reference from this thread to the collection before
+  // signaling the event, to ensure any reference taken by the callback, if any,
+  // would be the last one.
+  DestroyResourceCollection();
+  event.Signal();
+
+  CreateResourceCollection();
+  resource_collection_->ReceivedResources(resources);
+  resource_collection_->RefResources(resources);
+
+  // Destroy the collection before we have a chance to run the return callback.
+  ReturnCallback return_callback =
+      resource_collection_->GetReturnResourcesCallbackForImplThread();
+  resource_collection_->LoseAllResources();
+  DestroyResourceCollection();
+
+  EXPECT_TRUE(ReturnAndResetResourcesAvailable());
+  EXPECT_EQ(1u, returned_resources_.size());
+  EXPECT_EQ(444u, returned_resources_[0].id);
+  EXPECT_EQ(1, returned_resources_[0].count);
+  EXPECT_TRUE(returned_resources_[0].lost);
+  returned_resources_.clear();
+
+  thread.message_loop()->PostTask(FROM_HERE,
+                                  base::Bind(&ReturnResourcesOnThread,
+                                             return_callback,
+                                             returned_resources,
+                                             &event));
+  event.Signal();
+
+  thread.Stop();
+}
+
+}  // namespace
+}  // namespace cc