Allow MessageFilters to restrict listening to specific message classes

content/browser/renderer_host/media/midi_host.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/media/midi_host.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/debug/trace_event.h"
 #include "base/process/process.h"
@@ skipping 17 matching lines @@
 // The total number of bytes which we're allowed to send to the OS
 // before knowing that they have been successfully sent.
 const size_t kMaxInFlightBytes = 10 * 1024 * 1024;  // 10 MB.
 
 // We keep track of the number of bytes successfully sent to
 // the hardware.  Every once in a while we report back to the renderer
 // the number of bytes sent since the last report. This threshold determines
 // how many bytes will be sent before reporting back to the renderer.
 const size_t kAcknowledgementThresholdBytes = 1024 * 1024;  // 1 MB.
 
+const uint32 kFilteredMessageClasses[] = {
+  MidiMsgStart,
+};
+
 bool IsDataByte(uint8 data) {
   return (data & 0x80) == 0;
 }
 
 bool IsSystemRealTimeMessage(uint8 data) {
   return 0xf8 <= data && data <= 0xff;
 }
 
 }  // namespace
 
 using media::kSysExByte;
 using media::kEndOfSysExByte;
 
 MidiHost::MidiHost(int renderer_process_id, media::MidiManager* midi_manager)
-    : renderer_process_id_(renderer_process_id),
+    : BrowserMessageFilter(
+          kFilteredMessageClasses, arraysize(kFilteredMessageClasses)),
+      renderer_process_id_(renderer_process_id),
       has_sys_ex_permission_(false),
       midi_manager_(midi_manager),
       sent_bytes_in_flight_(0),
       bytes_sent_since_last_acknowledgement_(0) {
 }
 
 MidiHost::~MidiHost() {
   if (midi_manager_)
     midi_manager_->EndSession(this);
 }
@@ skipping 154 matching lines @@
     }
     waiting_data_length = media::GetMidiMessageLength(current);
     if (waiting_data_length == 0)
       return false;  // Error: |current| should have been a valid status byte.
     --waiting_data_length;  // Found status byte
   }
   return waiting_data_length == 0 && !in_sysex;
 }
 
 }  // namespace content