Call base for MediaControlPanelElement::RemovedFrom().

Things like the isConnected() flag was not updated for these elements
when removed.

Bug: 868810
Change-Id: I53aecf996c3d45253ab9929aa94cf29fd0c4ff6f
Reviewed-on: https://chromium-review.googlesource.com/1202063Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588948}

third_party/blink/renderer/modules/media_controls/elements/media_control_panel_element.cc

@@ -125,7 +125,8 @@ void MediaControlPanelElement::MakeTransparent() {
   opaque_ = false;
 }
 
-void MediaControlPanelElement::RemovedFrom(ContainerNode&) {
+void MediaControlPanelElement::RemovedFrom(ContainerNode& insertion_point) {
+  MediaControlDivElement::RemovedFrom(insertion_point);
   DetachTransitionEventListener();
 }
 

third_party/blink/renderer/modules/media_controls/elements/media_control_panel_element_test.cc

@@ -49,6 +49,7 @@ class MediaControlPanelElementTest : public PageTestBase {
   }
 
   MediaControlPanelElement& GetPanel() { return *panel_element_.Get(); }
+  HTMLMediaElement& GetMediaElement() { return *media_element_.Get(); }
 
  private:
   void TriggerEvent(const AtomicString& name) {
@@ -89,4 +90,12 @@ TEST_F(MediaControlPanelElementTest, StateTransitions) {
   ExpectPanelIsDisplayed();
 }
 
+TEST_F(MediaControlPanelElementTest, isConnected) {
+  EXPECT_TRUE(
+      GetMediaElement().GetMediaControls()->PanelElement()->isConnected());
+  GetMediaElement().remove();
+  EXPECT_FALSE(
+      GetMediaElement().GetMediaControls()->PanelElement()->isConnected());
+}
+
 }  // namespace blink