Bug 1331495 - Add an operator<< overload for TimeDuration. r=froydnj

MozReview-Commit-ID: dYKdlKI8Le

--HG--
extra : rebase_source : a56ed17f1c505ca50e3a9bb9ad0e34a1060ef1ac

mozglue/misc/TimeStamp.h

@@ -9,6 +9,7 @@
 
 #include <stdint.h>
 #include <algorithm>  // for std::min, std::max
+#include <ostream>
 #include "mozilla/Assertions.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/FloatingPoint.h"
@@ -279,6 +280,11 @@ public:
     return mValue != 0;
   }
 
+  friend std::ostream& operator<<(std::ostream& aStream,
+                                  const BaseTimeDuration& aDuration) {
+    return aStream << aDuration.ToMilliseconds() << " ms";
+  }
+
   // Return a best guess at the system's current timing resolution,
   // which might be variable.  BaseTimeDurations below this order of
   // magnitude are meaningless, and those at the same order of