Add UMA histograms for more detailed latency tracking on the CRD host.

remoting/protocol/host_event_dispatcher.h

Index: remoting/protocol/host_event_dispatcher.h
diff --git a/remoting/protocol/host_event_dispatcher.h b/remoting/protocol/host_event_dispatcher.h
index 3f1bd88c81ba30a6c8ad81e3903c02f329046f00..8fa35643241f39fc8ff1539300e6f0f20140e4b7 100644
--- a/remoting/protocol/host_event_dispatcher.h
+++ b/remoting/protocol/host_event_dispatcher.h
@@ -18,7 +18,7 @@ class InputStub;
 // channel to InputStub.
 class HostEventDispatcher : public ChannelDispatcherBase {
  public:
-  typedef base::Callback<void(int64)> EventTimestampCallback;
+  typedef base::Callback<void(int64_t)> OnInputEventCallback;
 
   HostEventDispatcher();
   ~HostEventDispatcher() override;
@@ -30,8 +30,8 @@ class HostEventDispatcher : public ChannelDispatcherBase {
 
   // Set callback to notify of each message's sequence number. The
   // callback cannot tear down this object.
-  void set_event_timestamp_callback(const EventTimestampCallback& value) {
-    event_timestamp_callback_ = value;
+  void set_on_input_event_callback(const OnInputEventCallback& value) {
+    on_input_event_callback_ = value;
   }
 
  private:
@@ -39,7 +39,7 @@ class HostEventDispatcher : public ChannelDispatcherBase {
                          const base::Closure& done_task);
 
   InputStub* input_stub_;
-  EventTimestampCallback event_timestamp_callback_;
+  OnInputEventCallback on_input_event_callback_;
 
   ProtobufMessageParser<EventMessage> parser_;