[jumbo] avoid MediaStubLocalFrameClient ambiguity

https://chromium-review.googlesource.com/c/chromium/src/+/996632 added
a MediaStubLocalFrameClient which conflicts with a preexisting class
in html_media_element_event_listeners_test.cc in jumbo builds.  Let's
rename this one.

TBR=mlamouri@chromium.org

Bug: 827396
Change-Id: If04b1de4a6cea922e5d88707505f1b0d69255f9c
Reviewed-on: https://chromium-review.googlesource.com/1005084
Commit-Queue: Mostyn Bramley-Moore <mostynb@vewd.com>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549708}

third_party/blink/renderer/core/html/media/html_media_element_test.cc

@@ -25,10 +25,10 @@ class MockWebMediaPlayer : public EmptyWebMediaPlayer {
   MOCK_CONST_METHOD0(CurrentTime, double());
 };
 
-class MediaStubLocalFrameClient : public EmptyLocalFrameClient {
+class WebMediaStubLocalFrameClient : public EmptyLocalFrameClient {
  public:
-  static MediaStubLocalFrameClient* Create() {
-    return new MediaStubLocalFrameClient;
+  static WebMediaStubLocalFrameClient* Create() {
+    return new WebMediaStubLocalFrameClient;
   }
 
   std::unique_ptr<WebMediaPlayer> CreateWebMediaPlayer(
@@ -46,7 +46,7 @@ class HTMLMediaElementTest : public testing::TestWithParam<MediaTestParam> {
  protected:
   void SetUp() override {
     dummy_page_holder_ = DummyPageHolder::Create(
-        IntSize(), nullptr, MediaStubLocalFrameClient::Create(), nullptr);
+        IntSize(), nullptr, WebMediaStubLocalFrameClient::Create(), nullptr);
 
     if (GetParam() == MediaTestParam::kAudio)
       media_ = HTMLAudioElement::Create(dummy_page_holder_->GetDocument());