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 a207659a4a922203a2e3850bbcdde4b1425dd21d..e3f928699b77cef9a15d92a229eb3483c384e6fe 100644
--- a/base/message_loop.cc
+++ b/base/message_loop.cc
@@ -303,20 +303,27 @@ void MessageLoop::PostNonNestableDelayedTask(
 }
 
 void MessageLoop::Run() {
-  AutoRunState save_state(this);
+  AutoRunState save_state(this, NULL);
+  RunHandler();
+}
+
+void MessageLoop::RunWithID(const RunID& run_id) {
+  AutoRunState save_state(this, run_id);
+  if (run_id->quit_now_received_)
+    return;
   RunHandler();
 }
 
 void MessageLoop::RunAllPending() {
-  AutoRunState save_state(this);
-  state_->quit_received = true;  // Means run until we would otherwise block.
+  AutoRunState save_state(this, NULL);
+  state_->quit_received_ = true;  // Means run until we would otherwise block.
   RunHandler();
 }
 
-void MessageLoop::Quit() {
+void MessageLoop::QuitWhenIdle() {
   DCHECK_EQ(this, current());
   if (state_) {
-    state_->quit_received = true;
+    state_->quit_received_ = true;
   } else {
     NOTREACHED() << "Must be inside Run to call Quit";
   }
@@ -331,13 +338,53 @@ void MessageLoop::QuitNow() {
   }
 }
 
-static void QuitCurrent() {
-  MessageLoop::current()->Quit();
+void MessageLoop::QuitNowWithID(const RunID& run_id) {
+  DCHECK_EQ(this, current());
+
+  // Set quit_now_received_ so that the corresponding Run scope is quit as soon
+  // as it is returned to. It's also possible that the corresponding Run has not
+  // begun; in that case, this will cause the Run to immediately return.
+  run_id->quit_now_received_ = true;
+
+  if (!state_)
+    return;
+
+  // If the state_ pointer matches that of the RunIDObject, we're at the same
+  // Run scope, so quit now.
+  if (state_ == run_id->run_state_)
+    QuitNow();
+}
+
+static void QuitCurrentWhenIdle() {
+  MessageLoop::current()->QuitWhenIdle();
+}
+
+static void QuitCurrentNow() {
+  MessageLoop::current()->QuitNow();
+}
+
+static void QuitCurrentNowWithID(const MessageLoop::RunID& run_id) {
+  MessageLoop::current()->QuitNowWithID(run_id);
+}
+
+// static
+base::Closure MessageLoop::QuitWhenIdleClosure() {
+  return base::Bind(&QuitCurrentWhenIdle);
 }
 
 // static
-base::Closure MessageLoop::QuitClosure() {
-  return base::Bind(&QuitCurrent);
+base::Closure MessageLoop::QuitNowClosure() {
+  return base::Bind(&QuitCurrentNow);
+}
+
+// static
+base::Closure MessageLoop::QuitNowWithIDClosure(
+    const RunID& run_id) {
+  return base::Bind(&QuitCurrentNowWithID, run_id);
+}
+
+MessageLoop::RunID MessageLoop::GetRunID() {
+  return new RunIDObject();
 }
 
 void MessageLoop::SetNestableTasksAllowed(bool allowed) {
@@ -355,7 +402,7 @@ bool MessageLoop::NestableTasksAllowed() const {
 }
 
 bool MessageLoop::IsNested() {
-  return state_->run_depth > 1;
+  return state_->run_depth_ > 1;
 }
 
 void MessageLoop::AddTaskObserver(TaskObserver* task_observer) {
@@ -414,9 +461,9 @@ void MessageLoop::RunInternal() {
   StartHistogrammer();
 
 #if !defined(OS_MACOSX) && !defined(OS_ANDROID)
-  if (state_->dispatcher && type() == TYPE_UI) {
+  if (state_->dispatcher_ && type() == TYPE_UI) {
     static_cast<base::MessagePumpForUI*>(pump_.get())->
-        RunWithDispatcher(this, state_->dispatcher);
+        RunWithDispatcher(this, state_->dispatcher_);
     return;
   }
 #endif
@@ -425,7 +472,7 @@ void MessageLoop::RunInternal() {
 }
 
 bool MessageLoop::ProcessNextDelayedNonNestableTask() {
-  if (state_->run_depth != 1)
+  if (state_->run_depth_ != 1)
     return false;
 
   if (deferred_non_nestable_work_queue_.empty())
@@ -473,7 +520,7 @@ 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 || state_->run_depth_ == 1) {
     RunTask(pending_task);
     // Show that we ran a task (Note: a new one might arrive as a
     // consequence!).
@@ -696,7 +743,7 @@ bool MessageLoop::DoIdleWork() {
   if (ProcessNextDelayedNonNestableTask())
     return true;
 
-  if (state_->quit_received)
+  if (state_->quit_received_)
     pump_->Quit();
 
   return false;
@@ -716,27 +763,51 @@ void MessageLoop::ReleaseSoonInternal(
 }
 
 //------------------------------------------------------------------------------
+// MessageLoop::RunState
+
+MessageLoop::RunState::RunState() {
+}
+
+MessageLoop::RunState::~RunState() {
+}
+
+//------------------------------------------------------------------------------
 // MessageLoop::AutoRunState
 
-MessageLoop::AutoRunState::AutoRunState(MessageLoop* loop) : loop_(loop) {
+MessageLoop::AutoRunState::AutoRunState(MessageLoop* loop, const RunID& run_id)
+    : loop_(loop) {
   // Make the loop reference us.
   previous_state_ = loop_->state_;
   if (previous_state_) {
-    run_depth = previous_state_->run_depth + 1;
+    run_depth_ = previous_state_->run_depth_ + 1;
   } else {
-    run_depth = 1;
+    run_depth_ = 1;
   }
   loop_->state_ = this;
 
+  if (run_id.get()) {
+    DCHECK(!run_id->used_);
+    run_state_id_ = run_id;
+    run_state_id_->used_ = true;
+    run_state_id_->run_state_ = this;
+  }
+
   // Initialize the other fields:
-  quit_received = false;
+  quit_received_ = false;
 #if !defined(OS_MACOSX) && !defined(OS_ANDROID)
-  dispatcher = NULL;
+  dispatcher_ = NULL;
 #endif
 }
 
 MessageLoop::AutoRunState::~AutoRunState() {
   loop_->state_ = previous_state_;
+  if (run_state_id_.get()) {
+    // run_state_id_->run_state_ points to 'this', so clear it.
+    run_state_id_->run_state_ = NULL;
+  }
+  if (previous_state_ && previous_state_->run_state_id_.get()
+      && previous_state_->run_state_id_->quit_now_received_)
+    MessageLoop::current()->QuitNow();
 }
 
 //------------------------------------------------------------------------------
@@ -765,15 +836,22 @@ void MessageLoopForUI::RemoveObserver(Observer* observer) {
 }
 
 void MessageLoopForUI::RunWithDispatcher(Dispatcher* dispatcher) {
-  AutoRunState save_state(this);
-  state_->dispatcher = dispatcher;
+  AutoRunState save_state(this, NULL);
+  state_->dispatcher_ = dispatcher;
+  RunHandler();
+}
+
+void MessageLoopForUI::RunWithDispatcher(Dispatcher* dispatcher,
+                                         const RunID& run_id) {
+  AutoRunState save_state(this, run_id);
+  state_->dispatcher_ = dispatcher;
   RunHandler();
 }
 
 void MessageLoopForUI::RunAllPendingWithDispatcher(Dispatcher* dispatcher) {
-  AutoRunState save_state(this);
-  state_->dispatcher = dispatcher;
-  state_->quit_received = true;  // Means run until we would otherwise block.
+  AutoRunState save_state(this, NULL);
+  state_->dispatcher_ = dispatcher;
+  state_->quit_received_ = true;  // Means run until we would otherwise block.
   RunHandler();
 }