High resolution timer fix for Windows

base/message_loop/message_loop.cc

Index: base/message_loop/message_loop.cc
diff --git a/base/message_loop/message_loop.cc b/base/message_loop/message_loop.cc
index 8e817dab8adece6ff025f277167901d6babdeab4..e783780d70b210933674fd0e42a733ce3ada2511 100644
--- a/base/message_loop/message_loop.cc
+++ b/base/message_loop/message_loop.cc
@@ -127,6 +127,7 @@ MessageLoop::DestructionObserver::~DestructionObserver() {
 
 MessageLoop::MessageLoop(Type type)
     : type_(type),
+      pending_high_res_tasks_(false),

[jamesr, 2014/07/18 04:45:37]

s/false/0/

[cpu_(ooo_6.6-7.5), 2014/07/18 22:53:10]

Done.

       nestable_tasks_allowed_(true),
 #if defined(OS_WIN)
       os_modal_loop_(false),
@@ -141,6 +142,7 @@ MessageLoop::MessageLoop(Type type)
 MessageLoop::MessageLoop(scoped_ptr<MessagePump> pump)
     : pump_(pump.Pass()),
       type_(TYPE_CUSTOM),
+      pending_high_res_tasks_(false),

[jamesr, 2014/07/18 04:45:37]

s/false/0/

[cpu_(ooo_6.6-7.5), 2014/07/18 22:53:10]

Done.

       nestable_tasks_allowed_(true),
 #if defined(OS_WIN)
       os_modal_loop_(false),
@@ -369,8 +371,8 @@ bool MessageLoop::is_running() const {
   return run_loop_ != NULL;
 }
 
-bool MessageLoop::IsHighResolutionTimerEnabledForTesting() {
-  return incoming_task_queue_->IsHighResolutionTimerEnabledForTesting();
+bool MessageLoop::HasHighResolutionTasks() {
+  return incoming_task_queue_->HasHighResolutionTasks();
 }
 
 bool MessageLoop::IsIdleForTesting() {
@@ -438,6 +440,11 @@ void MessageLoop::RunTask(const PendingTask& pending_task) {
       "src_file", pending_task.posted_from.file_name(),
       "src_func", pending_task.posted_from.function_name());
 
+  if (pending_task.is_high_res) {
+    pending_high_res_tasks_--;
+    CHECK(pending_high_res_tasks_ >= 0);
+  }
+
   DCHECK(nestable_tasks_allowed_);
   // Execute the task and assume the worst: It is probably not reentrant.
   nestable_tasks_allowed_ = false;
@@ -523,8 +530,10 @@ void MessageLoop::ReloadWorkQueue() {
   // |*work_queue| by waiting until the last minute (|*work_queue| is empty) to
   // load. That reduces the number of locks-per-task significantly when our
   // queues get large.
-  if (work_queue_.empty())
-    incoming_task_queue_->ReloadWorkQueue(&work_queue_);
+  if (work_queue_.empty()) {
+    pending_high_res_tasks_ +=
+        incoming_task_queue_->ReloadWorkQueue(&work_queue_);
+  }
 }
 
 void MessageLoop::ScheduleWork(bool was_empty) {
@@ -632,6 +641,15 @@ bool MessageLoop::DoIdleWork() {
   return false;
 }
 
+void MessageLoop::UpdateTimerGranularity() {
+#if defined(OS_WIN)
+  // Windows scheduler has by default ~15ms resolution. So, if we have high
+  // resolution tasks pending we need to temporarity increase the systemwide
+  // timer resolution to 1ms, and if we don't we need to go back to 15ms.
+  Time::ActivateHighResolutionTimer(pending_high_res_tasks_ > 0);
+#endif
+}
+
 void MessageLoop::DeleteSoonInternal(const tracked_objects::Location& from_here,
                                      void(*deleter)(const void*),
                                      const void* object) {