--- a/xpcom/ds/TimeStamp.h
+++ b/xpcom/ds/TimeStamp.h
@@ -87,18 +87,25 @@ public:
   TimeDuration& operator+=(const TimeDuration& aOther) {
     mValue += aOther.mValue;
     return *this;
   }
   TimeDuration& operator-=(const TimeDuration& aOther) {
     mValue -= aOther.mValue;
     return *this;
   }
-  TimeDuration operator*(const double aMultiplier) const {
-    return TimeDuration::FromTicks(mValue * int64_t(aMultiplier));
+
+private:
+  // Block double multiplier (slower, imprecise if long duration) - Bug 853398.
+  // If required, use MultDouble explicitly and with care.
+  TimeDuration operator*(const double aMultiplier) const MOZ_DELETE;
+
+public:
+  TimeDuration MultDouble(double aMultiplier) const {
+    return TimeDuration::FromTicks(static_cast<int64_t>(mValue * aMultiplier));
   }
   TimeDuration operator*(const int32_t aMultiplier) const {
     return TimeDuration::FromTicks(mValue * int64_t(aMultiplier));
   }
   TimeDuration operator*(const uint32_t aMultiplier) const {
     return TimeDuration::FromTicks(mValue * int64_t(aMultiplier));
   }
   TimeDuration operator*(const int64_t aMultiplier) const {