Handle repeated and overlapping (re)starts of mock speechrecognizer.

components/test_runner/mock_web_speech_recognizer.h

Index: components/test_runner/mock_web_speech_recognizer.h
diff --git a/components/test_runner/mock_web_speech_recognizer.h b/components/test_runner/mock_web_speech_recognizer.h
index 94c310618c9f19b5e3df3f5e2d47273e5531fb67..a25ea32af0829a75cfe36728324ddd3f1a1d9f58 100644
--- a/components/test_runner/mock_web_speech_recognizer.h
+++ b/components/test_runner/mock_web_speech_recognizer.h
@@ -71,6 +71,8 @@ class MockWebSpeechRecognizer : public blink::WebSpeechRecognizer {
   void PostRunTaskFromQueue();
   void RunTaskFromQueue();
 
+  bool HasPendingNewContextTasks() const;
+
   blink::WebSpeechRecognitionHandle handle_;
   blink::WebSpeechRecognizerClient* client_;
   std::vector<blink::WebString> mock_transcripts_;