tracing: remove WatchEvent feature

content/browser/tracing/tracing_controller_impl.h

Index: content/browser/tracing/tracing_controller_impl.h
diff --git a/content/browser/tracing/tracing_controller_impl.h b/content/browser/tracing/tracing_controller_impl.h
index 44b4c8f610018bef6af27960e64769ecf49b4a7b..a624b321d0695119a4ca6d984ac3ea84610dc504 100644
--- a/content/browser/tracing/tracing_controller_impl.h
+++ b/content/browser/tracing/tracing_controller_impl.h
@@ -73,10 +73,6 @@ class TracingControllerImpl
       const GetTraceBufferUsageCallback& callback) override;
   void AddMetadata(const base::DictionaryValue& metadata) override;
 
-  bool SetWatchEvent(const std::string& category_name,
-                     const std::string& event_name,
-                     const WatchEventCallback& callback) override;
-  bool CancelWatchEvent() override;
   bool IsTracing() const override;
 
   void RegisterTracingUI(TracingUI* tracing_ui);
@@ -144,10 +140,6 @@ class TracingControllerImpl
     return pending_trace_buffer_usage_callback_.is_null();
   }
 
-  bool can_cancel_watch_event() const {
-    return !watch_event_callback_.is_null();
-  }
-
   void PerformNextQueuedGlobalMemoryDump();
 
   // Methods for use by TraceMessageFilter.
@@ -188,8 +180,6 @@ class TracingControllerImpl
 
   void FinalizeGlobalMemoryDumpIfAllProcessesReplied();
 
-  void OnWatchEventMatched();
-
   void SetEnabledOnFileThread(
       const base::trace_event::TraceConfig& trace_config,
       int mode,
@@ -245,10 +235,6 @@ class TracingControllerImpl
   GetCategoriesDoneCallback pending_get_categories_done_callback_;
   GetTraceBufferUsageCallback pending_trace_buffer_usage_callback_;
 
-  std::string watch_category_name_;
-  std::string watch_event_name_;
-  WatchEventCallback watch_event_callback_;
-
   base::ObserverList<TraceMessageFilterObserver>
       trace_message_filter_observers_;