--- a/dom/events/EventListenerManager.cpp
+++ b/dom/events/EventListenerManager.cpp
@@ -96,16 +96,18 @@ EventListenerManager::EventListenerManag
   : mMayHavePaintEventListener(false)
   , mMayHaveMutationListeners(false)
   , mMayHaveCapturingListeners(false)
   , mMayHaveSystemGroupListeners(false)
   , mMayHaveTouchEventListener(false)
   , mMayHaveScrollWheelEventListener(false)
   , mMayHaveMouseEnterLeaveEventListener(false)
   , mMayHavePointerEnterLeaveEventListener(false)
+  , mMayHaveKeyEventListener(false)
+  , mMayHaveInputOrCompositionEventListener(false)
   , mClearingListeners(false)
   , mIsMainThreadELM(NS_IsMainThread())
   , mNoListenerForEvent(0)
   , mTarget(aTarget)
 {
   NS_ASSERTION(aTarget, "unexpected null pointer");
 
   if (mIsMainThreadELM) {
@@ -381,17 +383,31 @@ EventListenerManager::AddEventListenerIn
 #ifdef MOZ_GAMEPAD
   } else if (aType >= NS_GAMEPAD_START &&
              aType <= NS_GAMEPAD_END) {
     nsPIDOMWindow* window = GetInnerWindowForTarget();
     if (window) {
       window->SetHasGamepadEventListener();
     }
 #endif
+  } else if (aTypeAtom == nsGkAtoms::onkeydown ||
+             aTypeAtom == nsGkAtoms::onkeypress ||
+             aTypeAtom == nsGkAtoms::onkeyup) {
+    if (!aFlags.mInSystemGroup) {
+      mMayHaveKeyEventListener = true;
+    }
+  } else if (aTypeAtom == nsGkAtoms::oncompositionend ||
+             aTypeAtom == nsGkAtoms::oncompositionstart ||
+             aTypeAtom == nsGkAtoms::oncompositionupdate ||
+             aTypeAtom == nsGkAtoms::oninput) {
+    if (!aFlags.mInSystemGroup) {
+      mMayHaveInputOrCompositionEventListener = true;
+    }
   }
+
   if (aTypeAtom && mTarget) {
     mTarget->EventListenerAdded(aTypeAtom);
   }
 }
 
 bool
 EventListenerManager::IsDeviceType(uint32_t aType)
 {

--- a/dom/events/EventListenerManager.h
+++ b/dom/events/EventListenerManager.h
@@ -398,16 +398,29 @@ public:
    * Returns true if there may be a scroll wheel listener registered,
    * false if there definitely isn't.
    */
   bool MayHaveScrollWheelEventListener() { return mMayHaveScrollWheelEventListener; }
 
   bool MayHaveMouseEnterLeaveEventListener() { return mMayHaveMouseEnterLeaveEventListener; }
   bool MayHavePointerEnterLeaveEventListener() { return mMayHavePointerEnterLeaveEventListener; }
 
+  /**
+   * Returns true if there may be a key event listener (keydown, keypress,
+   * or keyup) registered, or false if there definitely isn't.
+   */
+  bool MayHaveKeyEventListener() { return mMayHaveKeyEventListener; }
+
+  /**
+   * Returns true if there may be an advanced input event listener (input,
+   * compositionstart, compositionupdate, or compositionend) registered,
+   * or false if there definitely isn't.
+   */
+  bool MayHaveInputOrCompositionEventListener() { return mMayHaveInputOrCompositionEventListener; }
+
   size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const;
 
   uint32_t ListenerCount() const
   {
     return mListeners.Length();
   }
 
   void MarkForCC();
@@ -548,19 +561,21 @@ protected:
   uint32_t mMayHavePaintEventListener : 1;
   uint32_t mMayHaveMutationListeners : 1;
   uint32_t mMayHaveCapturingListeners : 1;
   uint32_t mMayHaveSystemGroupListeners : 1;
   uint32_t mMayHaveTouchEventListener : 1;
   uint32_t mMayHaveScrollWheelEventListener : 1;
   uint32_t mMayHaveMouseEnterLeaveEventListener : 1;
   uint32_t mMayHavePointerEnterLeaveEventListener : 1;
+  uint32_t mMayHaveKeyEventListener : 1;
+  uint32_t mMayHaveInputOrCompositionEventListener : 1;
   uint32_t mClearingListeners : 1;
   uint32_t mIsMainThreadELM : 1;
-  uint32_t mNoListenerForEvent : 23;
+  uint32_t mNoListenerForEvent : 20;
 
   nsAutoTObserverArray<Listener, 2> mListeners;
   dom::EventTarget* mTarget;  // WEAK
   nsCOMPtr<nsIAtom> mNoListenerForEventAtom;
 
   friend class ELMCreationDetector;
   static uint32_t sMainThreadCreatedCount;
 };