--- a/content/media/webaudio/AudioEventTimeline.h
+++ b/content/media/webaudio/AudioEventTimeline.h
@@ -148,17 +148,29 @@ public:
   void SetValueCurveAtTime(const FloatArrayWrapper& aValues, float aStartTime, float aDuration, ErrorResult& aRv)
   {
     // TODO: implement
     // InsertEvent(Event(Event::SetValueCurve, aStartTime, 0.0f, 0.0f, aDuration, aValues), aRv);
   }
 
   void CancelScheduledValues(float aStartTime)
   {
-    // TODO: implement
+    for (unsigned i = 0; i < mEvents.Length(); ++i) {
+      if (mEvents[i].mTime >= aStartTime) {
+#ifdef DEBUG
+        // Sanity check: the array should be sorted, so all of the following
+        // events should have a time greater than aStartTime too.
+        for (unsigned j = i + 1; j < mEvents.Length(); ++j) {
+          MOZ_ASSERT(mEvents[j].mTime >= aStartTime);
+        }
+#endif
+        mEvents.TruncateLength(i);
+        break;
+      }
+    }
   }
 
   // This method computes the AudioParam value at a given time based on the event timeline
   float GetValueAtTime(float aTime) const
   {
     const Event* previous = nullptr;
     const Event* next = nullptr;
 

--- a/content/media/webaudio/compiledtest/TestAudioEventTimeline.cpp
+++ b/content/media/webaudio/compiledtest/TestAudioEventTimeline.cpp
@@ -203,16 +203,35 @@ void TestEventReplacement()
   is(timeline.GetEventCount(), 1, "Event should be replaced");
   is(timeline.GetValueAtTime(0.1f), 20.0f, "The first event should be overwritten");
   timeline.LinearRampToValueAtTime(30.0f, 0.1f, rv);
   is(rv, NS_OK, "Event scheduling should be successful");
   is(timeline.GetEventCount(), 2, "Different event type should be appended");
   is(timeline.GetValueAtTime(0.1f), 30.0f, "The first event should be overwritten");
 }
 
+void TestEventRemoval()
+{
+  Timeline timeline(10.0f, .1f, 20.0f);
+
+  ErrorResultMock rv;
+
+  timeline.SetValueAtTime(10.0f, 0.1f, rv);
+  timeline.SetValueAtTime(15.0f, 0.15f, rv);
+  timeline.SetValueAtTime(20.0f, 0.2f, rv);
+  timeline.LinearRampToValueAtTime(30.0f, 0.3f, rv);
+  is(timeline.GetEventCount(), 4, "Should have three events initially");
+  timeline.CancelScheduledValues(0.4f);
+  is(timeline.GetEventCount(), 4, "Trying to delete past the end of the array should have no effect");
+  timeline.CancelScheduledValues(0.3f);
+  is(timeline.GetEventCount(), 3, "Should successfully delete one event");
+  timeline.CancelScheduledValues(0.12f);
+  is(timeline.GetEventCount(), 1, "Should successfully delete two events");
+}
+
 void TestBeforeFirstEvent()
 {
   Timeline timeline(10.0f, .1f, 20.0f);
 
   ErrorResultMock rv;
 
   timeline.SetValueAtTime(20.0f, 1.0f, rv);
   is(timeline.GetValueAtTime(0.5f), 10.0f, "Retrun the default value before the first event");
@@ -322,16 +341,17 @@ int main()
   ScopedXPCOM xpcom("TestAudioEventTimeline");
   if (xpcom.failed()) {
     return 1;
   }
 
   TestSpecExample();
   TestInvalidEvents();
   TestEventReplacement();
+  TestEventRemoval();
   TestBeforeFirstEvent();
   TestAfterLastValueEvent();
   TestAfterLastTargetValueEvent();
   TestAfterLastTargetValueEventWithValueSet();
   TestValue();
   TestLinearRampAtZero();
   TestExponentialRampAtZero();
   TestLinearRampAtSameTime();

--- a/dom/webidl/AudioParam.webidl
+++ b/dom/webidl/AudioParam.webidl
@@ -32,12 +32,12 @@ interface AudioParam {
     void setTargetAtTime(float target, float startTime, float timeConstant);
 
     // Sets an array of arbitrary parameter values starting at time for the given duration. 
     // The number of values will be scaled to fit into the desired duration. 
     // [Throws]
     // void setValueCurveAtTime(Float32Array values, float startTime, float duration);
 
     // Cancels all scheduled parameter changes with times greater than or equal to startTime. 
-    // void cancelScheduledValues(float startTime);
+    void cancelScheduledValues(float startTime);
 
 };