MessagePumpDefault can spin for up to 1 ms on Windows

base/message_loop/message_pump_default.cc

Index: base/message_loop/message_pump_default.cc
diff --git a/base/message_loop/message_pump_default.cc b/base/message_loop/message_pump_default.cc
index 0fac8b3c9c9adbe7597b59096a30ba2a9ad7e935..3449aec8605b32e7eb868573144ecb45929809d7 100644
--- a/base/message_loop/message_pump_default.cc
+++ b/base/message_loop/message_pump_default.cc
@@ -4,6 +4,8 @@
 
 #include "base/message_loop/message_pump_default.h"
 
+#include <algorithm>
+
 #include "base/logging.h"
 #include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
@@ -54,7 +56,31 @@ void MessagePumpDefault::Run(Delegate* delegate) {
     } else {
       TimeDelta delay = delayed_work_time_ - TimeTicks::Now();
       if (delay > TimeDelta()) {
+#if defined(OS_WIN)
+        // TODO(stanisc): crbug.com/623223: Consider moving the OS_WIN specific
+        // logic into TimedWait implementation in waitable_event_win.cc.
+
+        // crbug.com/487724: on Windows, waiting for less than 1 ms results in
+        // returning from TimedWait promptly and spinning
+        // MessagePumpDefault::Run loop for up to 1 ms - until it is time to
+        // run a delayed task. |min_delay| is the minimum possible wait to
+        // to avoid the spinning.
+        constexpr TimeDelta min_delay = TimeDelta::FromMilliseconds(1);
+        do {
+          delay = std::max(delay, min_delay);
+          if (event_.TimedWait(delay))
+            break;
+
+          // TimedWait can time out earlier than the specified |delay| on
+          // Windows. It doesn't make sense to run the outer loop in that case
+          // because there isn't going to be any new work. It is less overhead
+          // to just go back to wait.
+          // In practice this inner wait loop might have up to 3 iterations.
+          delay = delayed_work_time_ - TimeTicks::Now();
+        } while (delay > TimeDelta());
+#else
         event_.TimedWait(delay);
+#endif
       } else {
         // It looks like delayed_work_time_ indicates a time in the past, so we
         // need to call DoDelayedWork now.