Add base::RunLoop and update ui_test_utils to use it to reduce flakiness

base/message_loop.cc

Index: base/message_loop.cc
diff --git a/base/message_loop.cc b/base/message_loop.cc
index b040ecc8a6bf5f9bdde0d8229bfe493a5afd5a65..0703631244a023c52716c9b3aba13f9792f12619 100644
--- a/base/message_loop.cc
+++ b/base/message_loop.cc
@@ -131,7 +131,6 @@ MessageLoop::MessageLoop(Type type)
       nestable_tasks_allowed_(true),
       exception_restoration_(false),
       message_histogram_(NULL),
-      state_(NULL),
 #ifdef OS_WIN
       os_modal_loop_(false),
 #endif  // OS_WIN
@@ -180,7 +179,7 @@ MessageLoop::MessageLoop(Type type)
 MessageLoop::~MessageLoop() {
   DCHECK_EQ(this, current());
 
-  DCHECK(!state_);
+  DCHECK(!run_loop_);
 
   // Clean up any unprocessed tasks, but take care: deleting a task could
   // result in the addition of more tasks (e.g., via DeleteSoon).  We set a
@@ -292,21 +291,99 @@ void MessageLoop::PostNonNestableDelayedTask(
   AddToIncomingQueue(&pending_task);
 }
 
+MessageLoop::RunLoop::RunLoop()
+    : loop_(MessageLoop::current()),
+      run_called_(false),
+      stop_called_(false),
+      running_(false),
+      run_depth_(0),
+      quit_when_idle_received_(false) {
+#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
+   dispatcher_ = NULL;
+#endif
+}
+
+#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
+MessageLoop::RunLoop::RunLoop(Dispatcher* dispatcher)
+    : loop_(MessageLoop::current()),
+      run_called_(false),
+      stop_called_(false),
+      running_(false),
+      run_depth_(0),
+      quit_when_idle_received_(false),
+      dispatcher_(dispatcher) {
+}
+#endif
+
+MessageLoop::RunLoop::~RunLoop() {
+}
+
+void MessageLoop::RunLoop::Run() {
+  if (!BeforeRun())
+    return;
+  loop_->RunHandler();
+  AfterRun();
+}
+
+void MessageLoop::RunLoop::RunUntilIdle() {
+  quit_when_idle_received_ = true;
+  Run();
+}
+
+void MessageLoop::RunLoop::Stop() {
+  stop_called_ = true;
+  if (running_ && loop_->run_loop_ == this) {
+    // This is the inner-most RunLoop, so quit now.
+    loop_->QuitNow();
+  }
+}
+
+base::Closure MessageLoop::RunLoop::StopClosure() {
+  return base::Bind(&RunLoop::Stop, AsWeakPtr());
+}
+
+bool MessageLoop::RunLoop::BeforeRun() {
+  DCHECK(!run_called_);
+  run_called_ = true;
+
+  // Allow Stop to be called before Run.
+  if (stop_called_)
+    return false;
+
+  // Push RunLoop stack:
+  previous_run_loop_ = loop_->run_loop_;
+  run_depth_ = previous_run_loop_? previous_run_loop_->run_depth_ + 1 : 1;
+  loop_->run_loop_ = AsWeakPtr();
+
+  running_ = true;
+  return true;
+}
+
+void MessageLoop::RunLoop::AfterRun() {
+  running_ = false;
+
+  // Pop RunLoop stack:
+  loop_->run_loop_ = previous_run_loop_;
+
+  // Execute deferred QuitNow, if any:
+  if (previous_run_loop_ && previous_run_loop_->stop_called_)
+    loop_->QuitNow();
+}
+
 void MessageLoop::Run() {
-  AutoRunState save_state(this);
-  RunHandler();
+  RunLoop run_loop;
+  run_loop.Run();
 }
 
 void MessageLoop::RunAllPending() {
-  AutoRunState save_state(this);
-  state_->quit_received = true;  // Means run until we would otherwise block.
-  RunHandler();
+  RunLoop run_loop;
+  run_loop.RunUntilIdle();
 }
 
-void MessageLoop::Quit() {
+void MessageLoop::QuitWhenIdle() {
   DCHECK_EQ(this, current());
-  if (state_) {
-    state_->quit_received = true;
+  if (run_loop_) {
+    run_loop_->quit_when_idle_received_ = true;
   } else {
     NOTREACHED() << "Must be inside Run to call Quit";
   }
@@ -314,20 +391,20 @@ void MessageLoop::Quit() {
 
 void MessageLoop::QuitNow() {
   DCHECK_EQ(this, current());
-  if (state_) {
+  if (run_loop_) {
     pump_->Quit();
   } else {
     NOTREACHED() << "Must be inside Run to call Quit";
   }
 }
 
-static void QuitCurrent() {
-  MessageLoop::current()->Quit();
+static void QuitCurrentWhenIdle() {
+  MessageLoop::current()->QuitWhenIdle();
 }
 
 // static
-base::Closure MessageLoop::QuitClosure() {
-  return base::Bind(&QuitCurrent);
+base::Closure MessageLoop::QuitWhenIdleClosure() {
+  return base::Bind(&QuitCurrentWhenIdle);
 }
 
 void MessageLoop::SetNestableTasksAllowed(bool allowed) {
@@ -345,7 +422,7 @@ bool MessageLoop::NestableTasksAllowed() const {
 }
 
 bool MessageLoop::IsNested() {
-  return state_->run_depth > 1;
+  return run_loop_->run_depth_ > 1;
 }
 
 void MessageLoop::AddTaskObserver(TaskObserver* task_observer) {
@@ -366,7 +443,7 @@ void MessageLoop::AssertIdle() const {
 
 bool MessageLoop::is_running() const {
   DCHECK_EQ(this, current());
-  return state_ != NULL;
+  return !!run_loop_;
 }
 
 //------------------------------------------------------------------------------
@@ -404,9 +481,9 @@ void MessageLoop::RunInternal() {
   StartHistogrammer();
 
 #if !defined(OS_MACOSX) && !defined(OS_ANDROID)
-  if (state_->dispatcher && type() == TYPE_UI) {
+  if (run_loop_->dispatcher_ && type() == TYPE_UI) {
     static_cast<base::MessagePumpForUI*>(pump_.get())->
-        RunWithDispatcher(this, state_->dispatcher);
+        RunWithDispatcher(this, run_loop_->dispatcher_);
     return;
   }
 #endif
@@ -415,10 +492,10 @@ void MessageLoop::RunInternal() {
 }
 
 bool MessageLoop::ProcessNextDelayedNonNestableTask() {
-  if (state_->run_depth != 1)
+  if (deferred_non_nestable_work_queue_.empty())
     return false;
 
-  if (deferred_non_nestable_work_queue_.empty())
+  if (run_loop_->run_depth_ != 1)
     return false;
 
   PendingTask pending_task = deferred_non_nestable_work_queue_.front();
@@ -463,7 +540,7 @@ void MessageLoop::RunTask(const PendingTask& pending_task) {
 }
 
 bool MessageLoop::DeferOrRunPendingTask(const PendingTask& pending_task) {
-  if (pending_task.nestable || state_->run_depth == 1) {
+  if (pending_task.nestable || run_loop_->run_depth_ == 1) {
     RunTask(pending_task);
     // Show that we ran a task (Note: a new one might arrive as a
     // consequence!).
@@ -685,7 +762,7 @@ bool MessageLoop::DoIdleWork() {
   if (ProcessNextDelayedNonNestableTask())
     return true;
 
-  if (state_->quit_received)
+  if (run_loop_->quit_when_idle_received_)
     pump_->Quit();
 
   return false;
@@ -705,30 +782,6 @@ void MessageLoop::ReleaseSoonInternal(
 }
 
 //------------------------------------------------------------------------------
-// MessageLoop::AutoRunState
-
-MessageLoop::AutoRunState::AutoRunState(MessageLoop* loop) : loop_(loop) {
-  // Make the loop reference us.
-  previous_state_ = loop_->state_;
-  if (previous_state_) {
-    run_depth = previous_state_->run_depth + 1;
-  } else {
-    run_depth = 1;
-  }
-  loop_->state_ = this;
-
-  // Initialize the other fields:
-  quit_received = false;
-#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
-  dispatcher = NULL;
-#endif
-}
-
-MessageLoop::AutoRunState::~AutoRunState() {
-  loop_->state_ = previous_state_;
-}
-
-//------------------------------------------------------------------------------
 // MessageLoopForUI
 
 #if defined(OS_WIN)
@@ -754,16 +807,13 @@ void MessageLoopForUI::RemoveObserver(Observer* observer) {
 }
 
 void MessageLoopForUI::RunWithDispatcher(Dispatcher* dispatcher) {
-  AutoRunState save_state(this);
-  state_->dispatcher = dispatcher;
-  RunHandler();
+  RunLoop run_loop(dispatcher);
+  run_loop.Run();
 }
 
 void MessageLoopForUI::RunAllPendingWithDispatcher(Dispatcher* dispatcher) {
-  AutoRunState save_state(this);
-  state_->dispatcher = dispatcher;
-  state_->quit_received = true;  // Means run until we would otherwise block.
-  RunHandler();
+  RunLoop run_loop(dispatcher);
+  run_loop.RunUntilIdle();
 }
 
 #endif  //  !defined(OS_MACOSX) && !defined(OS_NACL) && !defined(OS_ANDROID)