implement SetWatchEvent and WaitForEvent for trace-based-tests

chrome/test/base/tracing.cc

 // Copyright (c) 2012 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 "chrome/test/base/tracing.h"
 
 #include "base/debug/trace_event.h"
 #include "base/memory/singleton.h"
 #include "base/message_loop.h"
 #include "content/public/browser/trace_controller.h"
 #include "content/public/browser/trace_subscriber.h"
 #include "content/public/test/test_utils.h"
 
 namespace {
 
 class InProcessTraceController : public content::TraceSubscriber {
  public:
   static InProcessTraceController* GetInstance() {
     return Singleton<InProcessTraceController>::get();
   }
 
-  InProcessTraceController() {}
+  InProcessTraceController()
+      : is_waiting_on_watch_(false)
+      , got_watch_notification_(false) {}
   virtual ~InProcessTraceController() {}
 
   bool BeginTracing(const std::string& categories) {
     return content::TraceController::GetInstance()->BeginTracing(
         this, categories);
   }
 
+  bool BeginTracingWithWatch(const std::string& categories,
+                             const char* category_name,
+                             const char* event_name,
+                             int num_occurrences) {
+    return BeginTracing(categories) &&
+           content::TraceController::GetInstance()->SetWatchEvent(
+               this, category_name, event_name, num_occurrences);
+  }
+
+  bool WaitForWatchEvent(base::TimeDelta timeout) {
+    if (got_watch_notification_)
+      return true;
+
+    if (timeout != base::TimeDelta()) {
+      timer_.Start(FROM_HERE, timeout, this,
+                   &InProcessTraceController::Timeout);
+    }
+
+    is_waiting_on_watch_ = true;

[ccameron, 2012/08/21 01:06:34]

Race: we will use is_waiting_on_watch to see if it is safe to access
message_loop_runner_ (resulting in NULL pointer access).  I'd advocate making
these updates and checks atomic by putting them in a mutex.

[jbates, 2012/08/23 22:45:28]

As discussed, the missing detail is that these methods are all called on the UI
thread. Added some DCHECKs and comments to make that more clear.

+    message_loop_runner_ = new content::MessageLoopRunner;
+    message_loop_runner_->Run();
+    is_waiting_on_watch_ = false;
+
+    return got_watch_notification_;
+  }
+
   bool EndTracing(std::string* json_trace_output) {
     using namespace base::debug;
 
     TraceResultBuffer::SimpleOutput output;
     trace_buffer_.SetOutputCallback(output.GetCallback());
 
     trace_buffer_.Start();
     if (!content::TraceController::GetInstance()->EndTracingAsync(this))
       return false;
     // Wait for OnEndTracingComplete() to quit the message loop.
     // OnTraceDataCollected may be called multiple times while blocking here.
     message_loop_runner_ = new content::MessageLoopRunner;
     message_loop_runner_->Run();
     trace_buffer_.Finish();
     trace_buffer_.SetOutputCallback(TraceResultBuffer::OutputCallback());
 
     *json_trace_output = output.json_output;
+
+    // Watch notifications can occur during this method's message loop run, but
+    // not after, so clear them here.
+    got_watch_notification_ = false;
     return true;
   }
 
  private:
   friend struct DefaultSingletonTraits<InProcessTraceController>;
 
-  // TraceSubscriber
+  // TraceSubscriber implementation
   virtual void OnEndTracingComplete() OVERRIDE {
     message_loop_runner_->Quit();
   }
 
-  // TraceSubscriber
+  // TraceSubscriber implementation
   virtual void OnTraceDataCollected(
       const scoped_refptr<base::RefCountedString>& trace_fragment) OVERRIDE {
     trace_buffer_.AddFragment(trace_fragment->data());
   }
 
+  // TraceSubscriber implementation
+  virtual void OnEventWatchNotification() {
+    got_watch_notification_ = true;
+    timer_.Stop();
+    if (is_waiting_on_watch_)

[ccameron, 2012/08/21 01:06:34]

Race: is_waiting_in_watch_ can be true while message_loop_runner_ is still NULL
(see WaitForWatchEvent's assignment).

+      message_loop_runner_->Quit();
+  }
+
+  void Timeout() {
+    DCHECK(is_waiting_on_watch_);
+    message_loop_runner_->Quit();
+  }
+
   // For collecting trace data asynchronously.
   base::debug::TraceResultBuffer trace_buffer_;
 
   scoped_refptr<content::MessageLoopRunner> message_loop_runner_;
 
+  base::OneShotTimer<InProcessTraceController> timer_;
+
+  bool is_waiting_on_watch_;
+  bool got_watch_notification_;
+
   DISALLOW_COPY_AND_ASSIGN(InProcessTraceController);
 };
 
 }  // namespace
 
 namespace tracing {
 
 bool BeginTracing(const std::string& categories) {
   return InProcessTraceController::GetInstance()->BeginTracing(categories);
 }
 
+bool BeginTracingWithWatch(const std::string& categories,
+                           const char* category_name,
+                           const char* event_name,
+                           int num_occurrences) {
+  return InProcessTraceController::GetInstance()->BeginTracingWithWatch(
+      categories, category_name, event_name, num_occurrences);
+}
+
+bool WaitForWatchEvent(base::TimeDelta timeout) {
+  return InProcessTraceController::GetInstance()->WaitForWatchEvent(timeout);
+}
+
 bool EndTracing(std::string* json_trace_output) {
   return InProcessTraceController::GetInstance()->EndTracing(json_trace_output);
 }
 
 }  // namespace tracing