Make AudioParameters a class instead of a struct

content/common/view_messages.h

Index: content/common/view_messages.h
diff --git a/content/common/view_messages.h b/content/common/view_messages.h
index 2ef5024ac82d47957592d2b8cf3c1bbff2a57871..e032f99557cf79adb11702885727cc1517195816 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -25,6 +25,7 @@
 #include "ipc/ipc_channel_handle.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_platform_file.h"
+#include "media/base/channel_layout.h"
 #include "media/base/media_log_event.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebCompositionUnderline.h"
@@ -53,6 +54,7 @@
 
 #define IPC_MESSAGE_START ViewMsgStart
 
+IPC_ENUM_TRAITS(ChannelLayout)
 IPC_ENUM_TRAITS(CSSColors::CSSColorName)
 IPC_ENUM_TRAITS(NavigationGesture)
 IPC_ENUM_TRAITS(ViewMsg_Navigate_Type::Value)
@@ -680,9 +682,9 @@ IPC_SYNC_MESSAGE_CONTROL0_1(ViewHostMsg_GetHardwareInputSampleRate,
 IPC_SYNC_MESSAGE_CONTROL0_1(ViewHostMsg_GetHardwareSampleRate,
                             double /* sample_rate */)
 
-// Asks the browser for the default number of audio input channels.
-IPC_SYNC_MESSAGE_CONTROL0_1(ViewHostMsg_GetHardwareInputChannelCount,
-                            uint32 /* channels */)
+// Asks the browser for the default channel layout.
+IPC_SYNC_MESSAGE_CONTROL0_1(ViewHostMsg_GetHardwareInputChannelLayout,
+                            ChannelLayout /* channel layout */)
 
 // Asks the browser for CPU usage of the renderer process in percents.
 IPC_SYNC_MESSAGE_CONTROL0_1(ViewHostMsg_GetCPUUsage,