Bug 1148102: P3. Add TimeUnitToFrames method. r=jya

dom/media/VideoUtils.cpp

@@ -41,6 +41,11 @@ CheckedInt64 UsecsToFrames(int64_t aUsecs, uint32_t aRate) {
   return (CheckedInt64(aUsecs) * aRate) / USECS_PER_S;
 }
 
+// Format TimeUnit as number of frames at given rate.
+CheckedInt64 TimeUnitToFrames(const media::TimeUnit& aTime, uint32_t aRate) {
+  return UsecsToFrames(aTime.ToMicroseconds(), aRate);
+}
+
 nsresult SecondsToUsecs(double aSeconds, int64_t& aOutUsecs) {
   if (aSeconds * double(USECS_PER_S) > INT64_MAX) {
     return NS_ERROR_FAILURE;

dom/media/VideoUtils.h

@@ -140,6 +140,9 @@ media::TimeUnit FramesToTimeUnit(int64_t aFrames, uint32_t aRate);
 // overflow while calulating the conversion.
 CheckedInt64 UsecsToFrames(int64_t aUsecs, uint32_t aRate);
 
+// Format TimeUnit as number of frames at given rate.
+CheckedInt64 TimeUnitToFrames(const media::TimeUnit& aTime, uint32_t aRate);
+
 // Converts milliseconds to seconds.
 #define MS_TO_SECONDS(ms) ((double)(ms) / (PR_MSEC_PER_SEC))