--- a/layout/base/MobileViewportManager.cpp
+++ b/layout/base/MobileViewportManager.cpp
@@ -19,46 +19,43 @@
 
 static mozilla::LazyLogModule sApzMvmLog("apz.mobileviewport");
 #define MVM_LOG(...) MOZ_LOG(sApzMvmLog, LogLevel::Debug, (__VA_ARGS__))
 
 NS_IMPL_ISUPPORTS(MobileViewportManager, nsIDOMEventListener, nsIObserver)
 
 #define DOM_META_ADDED NS_LITERAL_STRING("DOMMetaAdded")
 #define DOM_META_CHANGED NS_LITERAL_STRING("DOMMetaChanged")
-#define FULL_ZOOM_CHANGE NS_LITERAL_STRING("FullZoomChange")
 #define LOAD NS_LITERAL_STRING("load")
 #define BEFORE_FIRST_PAINT NS_LITERAL_CSTRING("before-first-paint")
 
 using namespace mozilla;
 using namespace mozilla::dom;
 using namespace mozilla::layers;
 
 MobileViewportManager::MobileViewportManager(MVMContext* aContext)
     : mContext(aContext), mIsFirstPaint(false), mPainted(false) {
   MOZ_ASSERT(mContext);
 
   MVM_LOG("%p: creating with context %p\n", this, mContext.get());
 
   mContext->AddEventListener(DOM_META_ADDED, this, false);
   mContext->AddEventListener(DOM_META_CHANGED, this, false);
-  mContext->AddEventListener(FULL_ZOOM_CHANGE, this, false);
   mContext->AddEventListener(LOAD, this, true);
 
   mContext->AddObserver(this, BEFORE_FIRST_PAINT.Data(), false);
 }
 
 MobileViewportManager::~MobileViewportManager() = default;
 
 void MobileViewportManager::Destroy() {
   MVM_LOG("%p: destroying\n", this);
 
   mContext->RemoveEventListener(DOM_META_ADDED, this, false);
   mContext->RemoveEventListener(DOM_META_CHANGED, this, false);
-  mContext->RemoveEventListener(FULL_ZOOM_CHANGE, this, false);
   mContext->RemoveEventListener(LOAD, this, true);
 
   mContext->RemoveObserver(this, BEFORE_FIRST_PAINT.Data());
 
   mContext->Destroy();
   mContext = nullptr;
 }
 
@@ -127,19 +124,16 @@ MobileViewportManager::HandleEvent(dom::
   nsAutoString type;
   event->GetType(type);
 
   if (type.Equals(DOM_META_ADDED)) {
     HandleDOMMetaAdded();
   } else if (type.Equals(DOM_META_CHANGED)) {
     MVM_LOG("%p: got a dom-meta-changed event\n", this);
     RefreshViewportSize(mPainted);
-  } else if (type.Equals(FULL_ZOOM_CHANGE)) {
-    MVM_LOG("%p: got a full-zoom-change event\n", this);
-    RefreshViewportSize(false);
   } else if (type.Equals(LOAD)) {
     MVM_LOG("%p: got a load event\n", this);
     if (!mPainted) {
       // Load event got fired before the before-first-paint message
       SetInitialViewport();
     }
   }
   return NS_OK;