cc: Fix UAF in g_raster_required_for_activation_delay

cc/resources/raster_worker_pool.cc

Index: cc/resources/raster_worker_pool.cc
diff --git a/cc/resources/raster_worker_pool.cc b/cc/resources/raster_worker_pool.cc
index 255d5af5f71e16c5614a4dc6e85fda3e92e29610..34a34fc3e5b8daa458d34483e14a48b71f1cbe21 100644
--- a/cc/resources/raster_worker_pool.cc
+++ b/cc/resources/raster_worker_pool.cc
@@ -15,21 +15,13 @@
 namespace cc {
 namespace {
 
-// Synthetic delay for raster tasks that are required for activation. Global to
-// avoid static initializer on critical path.
-struct RasterRequiredForActivationSyntheticDelayInitializer {
-  RasterRequiredForActivationSyntheticDelayInitializer()
-      : delay(base::debug::TraceEventSyntheticDelay::Lookup(
-            "cc.RasterRequiredForActivation")) {}
-  base::debug::TraceEventSyntheticDelay* delay;
-};
-static base::LazyInstance<RasterRequiredForActivationSyntheticDelayInitializer>
-    g_raster_required_for_activation_delay = LAZY_INSTANCE_INITIALIZER;
-
 class RasterTaskGraphRunner : public TaskGraphRunner,
                               public base::DelegateSimpleThread::Delegate {
  public:
-  RasterTaskGraphRunner() {
+  RasterTaskGraphRunner()
+      : trace_event_synthetic_delay_(
+            base::debug::TraceEventSyntheticDelay::Lookup(
+                "cc.RasterRequiredForActivation")) {
     size_t num_threads = RasterWorkerPool::GetNumRasterThreads();
     while (workers_.size() < num_threads) {
       scoped_ptr<base::DelegateSimpleThread> worker =
@@ -48,6 +40,10 @@ class RasterTaskGraphRunner : public TaskGraphRunner,
 
   virtual ~RasterTaskGraphRunner() { NOTREACHED(); }
 
+  base::debug::TraceEventSyntheticDelay* trace_event_synthetic_delay() const {
+    return trace_event_synthetic_delay_;
+  }
+
  private:
   // Overridden from base::DelegateSimpleThread::Delegate:
   virtual void Run() OVERRIDE {
@@ -55,6 +51,7 @@ class RasterTaskGraphRunner : public TaskGraphRunner,
   }
 
   ScopedPtrDeque<base::DelegateSimpleThread> workers_;
+  base::debug::TraceEventSyntheticDelay* trace_event_synthetic_delay_;

[reveman, 2014/08/27 00:34:37]

I think |synthetic_delay_| is verbose enough.

[boliu, 2014/08/27 01:14:49]

Done.

 };
 
 base::LazyInstance<RasterTaskGraphRunner>::Leaky g_task_graph_runner =
@@ -103,13 +100,14 @@ class RasterRequiredForActivationFinishedTaskImpl
   RasterRequiredForActivationFinishedTaskImpl(
       base::SequencedTaskRunner* task_runner,
       const base::Closure& on_raster_finished_callback,
-      size_t tasks_required_for_activation_count)
+      size_t tasks_required_for_activation_count,
+      base::debug::TraceEventSyntheticDelay* delay)
       : RasterFinishedTaskImpl(task_runner, on_raster_finished_callback),
+        delay_(delay),
         tasks_required_for_activation_count_(
             tasks_required_for_activation_count) {
     if (tasks_required_for_activation_count_) {
-      g_raster_required_for_activation_delay.Get().delay->BeginParallel(
-          &activation_delay_end_time_);
+      delay_->BeginParallel(&activation_delay_end_time_);
     }
   }
 
@@ -119,8 +117,7 @@ class RasterRequiredForActivationFinishedTaskImpl
         "cc", "RasterRequiredForActivationFinishedTaskImpl::RunOnWorkerThread");
 
     if (tasks_required_for_activation_count_) {
-      g_raster_required_for_activation_delay.Get().delay->EndParallel(
-          activation_delay_end_time_);
+      delay_->EndParallel(activation_delay_end_time_);
     }
     RasterFinished();
   }
@@ -128,6 +125,7 @@ class RasterRequiredForActivationFinishedTaskImpl
  private:
   virtual ~RasterRequiredForActivationFinishedTaskImpl() {}
 
+  base::debug::TraceEventSyntheticDelay* delay_;

[reveman, 2014/08/27 00:34:37]

How about just using g_task_graph_runner.Get().synthetic_delay() above instead?
Technically a bit more efficient as we don't have to access
g_task_graph_runner.Get() each time we create one of these tasks and that's good
as we'll create many more of these tasks than we run.

[boliu, 2014/08/27 01:14:49]

Done.

   base::TimeTicks activation_delay_end_time_;
   const size_t tasks_required_for_activation_count_;
 
@@ -191,7 +189,8 @@ RasterWorkerPool::CreateRasterRequiredForActivationFinishedTask(
   return make_scoped_refptr(new RasterRequiredForActivationFinishedTaskImpl(
       task_runner,
       on_raster_finished_callback,
-      tasks_required_for_activation_count));
+      tasks_required_for_activation_count,
+      g_task_graph_runner.Get().trace_event_synthetic_delay()));
 }
 
 // static