[Windows] Fix for Browser IO MessageLoop spinning the CPU.

base/message_loop/message_pump_win.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 "base/message_loop/message_pump_win.h"
 
+#include <limits>
 #include <math.h>
 
 #include "base/debug/trace_event.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/process/memory.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/strings/stringprintf.h"
 #include "base/win/wrapped_window_proc.h"
 
@@ skipping 46 matching lines @@
 int MessagePumpWin::GetCurrentDelay() const {
   if (delayed_work_time_.is_null())
     return -1;
 
   // Be careful here.  TimeDelta has a precision of microseconds, but we want a
   // value in milliseconds.  If there are 5.5ms left, should the delay be 5 or
   // 6?  It should be 6 to avoid executing delayed work too early.
   double timeout =
       ceil((delayed_work_time_ - TimeTicks::Now()).InMillisecondsF());
 
-  // If this value is negative, then we need to run delayed work soon.
-  int delay = static_cast<int>(timeout);
-  if (delay < 0)
-    delay = 0;
-
-  return delay;
+  // Range check the |timeout| while converting to an integer.  If the |timeout|
+  // is negative, then we need to run delayed work soon.  If the |timeout| is
+  // "overflowingly" large, that means a delayed task was posted with a
+  // super-long delay.
+  return timeout < 0 ? 0 :
+      (timeout > std::numeric_limits<int>::max() ?

[darin (slow to review), 2015/01/27 07:52:39]

you didn't want to use the max_int / 2 comparison here?

+       std::numeric_limits<int>::max() : static_cast<int>(timeout));
 }
 
 //-----------------------------------------------------------------------------
 // MessagePumpForUI public:
 
 MessagePumpForUI::MessagePumpForUI()
     : atom_(0) {
   InitMessageWnd();
 }
 
@@ skipping 564 matching lines @@
 
 // static
 MessagePumpForIO::IOHandler* MessagePumpForIO::KeyToHandler(
     ULONG_PTR key,
     bool* has_valid_io_context) {
   *has_valid_io_context = ((key & 1) == 0);
   return reinterpret_cast<IOHandler*>(key & ~static_cast<ULONG_PTR>(1));
 }
 
 }  // namespace base