--- a/dom/media/VideoUtils.cpp
+++ b/dom/media/VideoUtils.cpp
@@ -1,14 +1,17 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "VideoUtils.h"
 
+#include <functional>
+#include <stdint.h>
+
 #include "ImageContainer.h"
 #include "MediaContainerType.h"
 #include "MediaPrefs.h"
 #include "MediaResource.h"
 #include "TimeUnits.h"
 #include "VorbisUtils.h"
 #include "mozilla/Base64.h"
 #include "mozilla/SharedThreadPool.h"
@@ -20,31 +23,33 @@
 #include "nsContentTypeParser.h"
 #include "nsIConsoleService.h"
 #include "nsIRandomGenerator.h"
 #include "nsIServiceManager.h"
 #include "nsMathUtils.h"
 #include "nsServiceManagerUtils.h"
 #include "nsThreadUtils.h"
 
-#include <functional>
-#include <stdint.h>
-
 namespace mozilla {
 
 NS_NAMED_LITERAL_CSTRING(kEMEKeySystemClearkey, "org.w3.clearkey");
 NS_NAMED_LITERAL_CSTRING(kEMEKeySystemWidevine, "com.widevine.alpha");
 
 using layers::PlanarYCbCrImage;
 using media::TimeUnit;
 
-CheckedInt64 SaferMultDiv(int64_t aValue, uint32_t aMul, uint32_t aDiv) {
-  int64_t major = aValue / aDiv;
-  int64_t remainder = aValue % aDiv;
-  return CheckedInt64(remainder) * aMul / aDiv + CheckedInt64(major) * aMul;
+CheckedInt64 SaferMultDiv(int64_t aValue, uint64_t aMul, uint64_t aDiv) {
+  if (aMul > INT64_MAX || aDiv > INT64_MAX) {
+    return CheckedInt64(INT64_MAX) + 1; // Return an invalid checked int.
+  }
+  int64_t mul = aMul;
+  int64_t div = aDiv;
+  int64_t major = aValue / div;
+  int64_t remainder = aValue % div;
+  return CheckedInt64(remainder) * mul / div + CheckedInt64(major) * mul;
 }
 
 // Converts from number of audio frames to microseconds, given the specified
 // audio rate.
 CheckedInt64 FramesToUsecs(int64_t aFrames, uint32_t aRate) {
   return SaferMultDiv(aFrames, USECS_PER_S, aRate);
 }
 

--- a/dom/media/VideoUtils.h
+++ b/dom/media/VideoUtils.h
@@ -121,17 +121,17 @@ media::TimeIntervals GetEstimatedBuffere
 // Converts from number of audio frames (aFrames) to microseconds, given
 // the specified audio rate (aRate).
 CheckedInt64 FramesToUsecs(int64_t aFrames, uint32_t aRate);
 // Converts from number of audio frames (aFrames) TimeUnit, given
 // the specified audio rate (aRate).
 media::TimeUnit FramesToTimeUnit(int64_t aFrames, uint32_t aRate);
 // Perform aValue * aMul / aDiv, reducing the possibility of overflow due to
 // aValue * aMul overflowing.
-CheckedInt64 SaferMultDiv(int64_t aValue, uint32_t aMul, uint32_t aDiv);
+CheckedInt64 SaferMultDiv(int64_t aValue, uint64_t aMul, uint64_t aDiv);
 
 // Converts from microseconds (aUsecs) to number of audio frames, given the
 // specified audio rate (aRate). Stores the result in aOutFrames. Returns
 // true if the operation succeeded, or false if there was an integer
 // overflow while calulating the conversion.
 CheckedInt64 UsecsToFrames(int64_t aUsecs, uint32_t aRate);
 
 // Format TimeUnit as number of frames at given rate.