Base: Truncate the timeout of WaitableEvent::TimedWait on Windows.

base/synchronization/waitable_event_win.cc

 // Copyright (c) 2011 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/synchronization/waitable_event.h"
 
 #include <windows.h>
 
 #include "base/logging.h"
 #include "base/numerics/safe_conversions.h"
@@ skipping 33 matching lines @@
   base::ThreadRestrictions::AssertWaitAllowed();
   DWORD result = WaitForSingleObject(handle_.Get(), INFINITE);
   // It is most unexpected that this should ever fail.  Help consumers learn
   // about it if it should ever fail.
   DCHECK_EQ(WAIT_OBJECT_0, result) << "WaitForSingleObject failed";
 }
 
 bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
   base::ThreadRestrictions::AssertWaitAllowed();
   DCHECK_GE(max_time, TimeDelta());
-  // Be careful here.  TimeDelta has a precision of microseconds, but this API
-  // is in milliseconds.  If there are 5.5ms left, should the delay be 5 or 6?
-  // It should be 6 to avoid returning too early.
-  DWORD timeout = saturated_cast<DWORD>(max_time.InMillisecondsRoundedUp());
+  // Truncate the timeout to milliseconds. The API specifies that this method
+  // can return in less than |max_time| (when returning false), as the argument
+  // is the maximum time that a caller is willing to wait.
+  DWORD timeout = saturated_cast<DWORD>(max_time.InMilliseconds());
 
   DWORD result = WaitForSingleObject(handle_.Get(), timeout);
   switch (result) {
     case WAIT_OBJECT_0:
       return true;
     case WAIT_TIMEOUT:
       return false;
   }
   // It is most unexpected that this should ever fail.  Help consumers learn
   // about it if it should ever fail.
@@ skipping 19 matching lines @@
                              INFINITE);  // no timeout
   if (result >= WAIT_OBJECT_0 + count) {
     DPLOG(FATAL) << "WaitForMultipleObjects failed";
     return 0;
   }
 
   return result - WAIT_OBJECT_0;
 }
 
 }  // namespace base