media: Fix WebMediaPlayerImplTest.Encrypted test flakiness

The current test has a race condition that by the time MetaData is
reported (right after Demuxer initialization), the Renderer might not
have been initialized (which triggers the "waitingforkey" event, that
will trigger DidBlockPlaybackWaitingForKey().

This CL fixes the test so that Load() will wait for
DidBlockPlaybackWaitingForKey() to avoid this race condition.

Bug: 1021574
Test: Fix flaky test.
Change-Id: Icd3bdae9ceb2a5bb7791418e729e68e323ff74fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1900158Reviewed-by: John Rummell <jrummell@chromium.org>
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712709}

media/blink/webmediaplayer_impl_unittest.cc

@@ -1588,12 +1588,16 @@ TEST_F(WebMediaPlayerImplTest, Encrypted) {
   // To avoid PreloadMetadataLazyLoad.
   wmpi_->SetPreload(blink::WebMediaPlayer::kPreloadAuto);
 
-  EXPECT_CALL(encrypted_client_, DidBlockPlaybackWaitingForKey());
-  EXPECT_CALL(encrypted_client_, DidResumePlaybackBlockedForKey());
+  {
+    base::RunLoop run_loop;
     EXPECT_CALL(encrypted_client_,
                 Encrypted(EmeInitDataType::WEBM, NotNull(), Gt(0u)));
-  LoadAndWaitForReadyState(kEncryptedVideoOnlyTestFile,
-                           blink::WebMediaPlayer::kReadyStateHaveMetadata);
+    EXPECT_CALL(encrypted_client_, DidBlockPlaybackWaitingForKey());
+    EXPECT_CALL(encrypted_client_, DidResumePlaybackBlockedForKey())
+        .WillRepeatedly(RunClosure(run_loop.QuitClosure()));
+    Load(kEncryptedVideoOnlyTestFile);
+    run_loop.Run();
+  }
 
   CreateCdm();
 
@@ -1603,7 +1607,9 @@ TEST_F(WebMediaPlayerImplTest, Encrypted) {
       .WillRepeatedly(Return(nullptr));
   mock_cdm_context_.set_cdm_id(CdmContext::kInvalidCdmId);
 
-  // Wait for kNetworkStateFormatError caused by Renderer initialization error.
+  {
+    // Wait for kNetworkStateFormatError caused by Renderer initialization
+    // error.
     base::RunLoop run_loop;
     EXPECT_CALL(client_, NetworkStateChanged()).WillOnce(Invoke([&] {
       if (wmpi_->GetNetworkState() ==
@@ -1612,6 +1618,7 @@ TEST_F(WebMediaPlayerImplTest, Encrypted) {
     }));
     SetCdm();
     run_loop.Run();
+  }
 }
 
 TEST_F(WebMediaPlayerImplTest, Waiting_NoDecryptionKey) {