--- a/dom/html/TextTrackManager.cpp
+++ b/dom/html/TextTrackManager.cpp
@@ -306,16 +306,18 @@ void TextTrackManager::PopulatePendingLi
       mPendingTextTracks->AddTextTrack(ttrack,
                                        CompareTextTracks(mMediaElement));
     }
   }
 }
 
 void TextTrackManager::AddListeners() {
   if (mMediaElement) {
+    mMediaElement->AddEventListener(NS_LITERAL_STRING("resizecaption"), this,
+                                    false, false);
     mMediaElement->AddEventListener(NS_LITERAL_STRING("resizevideocontrols"),
                                     this, false, false);
     mMediaElement->AddEventListener(NS_LITERAL_STRING("seeked"), this, false,
                                     false);
     mMediaElement->AddEventListener(NS_LITERAL_STRING("controlbarchange"), this,
                                     false, true);
   }
 }
@@ -411,24 +413,30 @@ void TextTrackManager::GetTextTracksOfKi
 NS_IMETHODIMP
 TextTrackManager::HandleEvent(Event* aEvent) {
   if (!mTextTracks) {
     return NS_OK;
   }
 
   nsAutoString type;
   aEvent->GetType(type);
-  if (type.EqualsLiteral("resizevideocontrols") ||
-      type.EqualsLiteral("seeked")) {
+  WEBVTT_LOG("Handle event %s", NS_ConvertUTF16toUTF8(type).get());
+
+  const bool setDirty = type.EqualsLiteral("seeked") ||
+                        type.EqualsLiteral("resizecaption") ||
+                        type.EqualsLiteral("resizevideocontrols");
+  const bool updateDisplay = type.EqualsLiteral("controlbarchange") ||
+                             type.EqualsLiteral("resizecaption");
+
+  if (setDirty) {
     for (uint32_t i = 0; i < mTextTracks->Length(); i++) {
       ((*mTextTracks)[i])->SetCuesDirty();
     }
   }
-
-  if (type.EqualsLiteral("controlbarchange")) {
+  if (updateDisplay) {
     UpdateCueDisplay();
   }
 
   return NS_OK;
 }
 
 class SimpleTextTrackEvent : public Runnable {
  public:

--- a/layout/generic/nsVideoFrame.cpp
+++ b/layout/generic/nsVideoFrame.cpp
@@ -233,28 +233,29 @@ already_AddRefed<Layer> nsVideoFrame::Bu
 
   uint32_t flags = element->HasAlpha() ? 0 : Layer::CONTENT_OPAQUE;
   layer->SetContentFlags(flags);
 
   RefPtr<Layer> result = layer.forget();
   return result.forget();
 }
 
-class DispatchResizeToControls : public Runnable {
+class DispatchResizeEvent : public Runnable {
  public:
-  explicit DispatchResizeToControls(nsIContent* aContent)
-      : mozilla::Runnable("DispatchResizeToControls"), mContent(aContent) {}
+  explicit DispatchResizeEvent(nsIContent* aContent, const nsString& aName)
+      : mozilla::Runnable("DispatchResizeEvent"),
+        mContent(aContent),
+        mName(aName) {}
   NS_IMETHOD Run() override {
-    nsContentUtils::DispatchTrustedEvent(
-        mContent->OwnerDoc(), mContent,
-        NS_LITERAL_STRING("resizevideocontrols"), CanBubble::eNo,
-        Cancelable::eNo);
+    nsContentUtils::DispatchTrustedEvent(mContent->OwnerDoc(), mContent, mName,
+                                         CanBubble::eNo, Cancelable::eNo);
     return NS_OK;
   }
   nsCOMPtr<nsIContent> mContent;
+  nsString mName;
 };
 
 void nsVideoFrame::Reflow(nsPresContext* aPresContext, ReflowOutput& aMetrics,
                           const ReflowInput& aReflowInput,
                           nsReflowStatus& aStatus) {
   MarkInReflow();
   DO_GLOBAL_REFLOW_COUNT("nsVideoFrame");
   DISPLAY_REFLOW(aPresContext, this, aReflowInput, aMetrics, aStatus);
@@ -349,20 +350,22 @@ void nsVideoFrame::Reflow(nsPresContext*
           contentBoxBSize = myWM.IsOrthogonalTo(wm) ? kidDesiredSize.ISize(wm)
                                                     : kidDesiredSize.BSize(wm);
         }
       }
 
       FinishReflowChild(child, aPresContext, kidDesiredSize, &kidReflowInput,
                         borderPadding.left, borderPadding.top, 0);
 
-      if (child->GetContent() == videoControlsDiv &&
-          child->GetSize() != oldChildSize) {
+      if (child->GetSize() != oldChildSize) {
+        const nsString name = child->GetContent() == videoControlsDiv
+                                  ? NS_LITERAL_STRING("resizevideocontrols")
+                                  : NS_LITERAL_STRING("resizecaption");
         RefPtr<Runnable> event =
-            new DispatchResizeToControls(child->GetContent());
+            new DispatchResizeEvent(child->GetContent(), name);
         nsContentUtils::AddScriptRunner(event);
       }
     } else {
       NS_ERROR("Unexpected extra child frame in nsVideoFrame; skipping");
     }
   }
 
   if (isBSizeShrinkWrapping) {