Adds proper IPC usage for AudioDevice::GetAudioHardwareBufferSize().

content/browser/renderer_host/render_message_filter.cc

Index: content/browser/renderer_host/render_message_filter.cc
===================================================================
--- content/browser/renderer_host/render_message_filter.cc	(revision 109200)
+++ content/browser/renderer_host/render_message_filter.cc	(working copy)
@@ -356,6 +356,8 @@
                         OnCacheableMetadataAvailable)
     IPC_MESSAGE_HANDLER_DELAY_REPLY(ViewHostMsg_Keygen, OnKeygen)
     IPC_MESSAGE_HANDLER(ViewHostMsg_AsyncOpenFile, OnAsyncOpenFile)
+    IPC_MESSAGE_HANDLER(ViewHostMsg_GetHardwareBufferSize,
+                        OnGetHardwareBufferSize)
     IPC_MESSAGE_HANDLER(ViewHostMsg_GetHardwareInputSampleRate,
                         OnGetHardwareInputSampleRate)
     IPC_MESSAGE_HANDLER(ViewHostMsg_GetHardwareSampleRate,
@@ -606,6 +608,10 @@
   *route_id = render_widget_helper_->GetNextRoutingID();
 }
 
+void RenderMessageFilter::OnGetHardwareBufferSize(uint32* buffer_size) {
+  *buffer_size = static_cast<uint32>(media::GetAudioHardwareBufferSize());
+}
+
 void RenderMessageFilter::OnGetHardwareInputSampleRate(double* sample_rate) {
   *sample_rate = media::GetAudioInputHardwareSampleRate();
 }