[TTS] Adjust WeakPtr lifetime to object lifetime of TtsMessageFilter

chrome/browser/speech/tts_message_filter.h

Index: chrome/browser/speech/tts_message_filter.h
diff --git a/chrome/browser/speech/tts_message_filter.h b/chrome/browser/speech/tts_message_filter.h
index cecb2ba6dc32dc698fa2403e9ffa2ecde4b17ffc..8059778a91fffa8d3b190a443c546e5b7d159a4a 100644
--- a/chrome/browser/speech/tts_message_filter.h
+++ b/chrome/browser/speech/tts_message_filter.h
@@ -17,8 +17,7 @@ class BrowserContext;
 class TtsMessageFilter
     : public content::BrowserMessageFilter,
       public UtteranceEventDelegate,
-      public VoicesChangedDelegate,
-      public base::SupportsWeakPtr<TtsMessageFilter> {
+      public VoicesChangedDelegate {
  public:
   explicit TtsMessageFilter(int render_process_id,
       content::BrowserContext* browser_context);
@@ -57,6 +56,8 @@ class TtsMessageFilter
   int render_process_id_;
   content::BrowserContext* browser_context_;
 
+  base::WeakPtrFactory<TtsMessageFilter> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(TtsMessageFilter);
 };