Replace WebAudio MediaCodec usage with FFmpeg. A ~4x improvement.

content/common/view_messages.h

 // Copyright (c) 2012 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.
 
 // IPC messages for page rendering.
 // Multiply-included message file, hence no include guard.
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 1371 matching lines @@
 IPC_MESSAGE_ROUTED3(ViewHostMsg_FindMatchRects_Reply,
                     int /* version */,
                     std::vector<gfx::RectF> /* rects */,
                     gfx::RectF /* active_rect */)
 
 // Start an android intent with the given URI.
 IPC_MESSAGE_ROUTED2(ViewHostMsg_StartContentIntent,
                     GURL /* content_url */,
                     bool /* is_main_frame */)
 
-// This message runs the MediaCodec for decoding audio for webaudio.
-IPC_MESSAGE_CONTROL3(ViewHostMsg_RunWebAudioMediaCodec,
-                     base::SharedMemoryHandle /* encoded_data_handle */,
-                     base::FileDescriptor /* pcm_output */,
-                     uint32_t /* data_size*/)
-
 // Reply to the ViewMsg_ExtractSmartClipData message.
 IPC_MESSAGE_ROUTED3(ViewHostMsg_SmartClipDataExtracted,
                     base::string16 /* text */,
                     base::string16 /* html */,
                     gfx::Rect /* rect */)
 
 // Notifies that an unhandled tap has occurred at the specified x,y position
 // and that the UI may need to be triggered.
 IPC_MESSAGE_ROUTED2(ViewHostMsg_ShowUnhandledTapUIIfNeeded,
                     int /* x */,
                     int /* y */)
 
 #elif defined(OS_MACOSX)
 // Informs the browser that a plugin has gained or lost focus.
 IPC_MESSAGE_ROUTED2(ViewHostMsg_PluginFocusChanged,
                     bool, /* focused */
                     int /* plugin_id */)
 
 // Instructs the browser to start plugin IME.
 IPC_MESSAGE_ROUTED0(ViewHostMsg_StartPluginIme)
 
 // Receives content of a web page as plain text.
 IPC_MESSAGE_ROUTED1(ViewMsg_GetRenderedTextCompleted, std::string)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent ViewMsg, then ifdefs for platform specific ViewMsg, then platform
 // independent ViewHostMsg, then ifdefs for platform specific ViewHostMsg.