Introduce PPB_AudioInput_Dev v0.3 and refactor the device enumeration code:

ppapi/proxy/plugin_dispatcher.cc

Index: ppapi/proxy/plugin_dispatcher.cc
diff --git a/ppapi/proxy/plugin_dispatcher.cc b/ppapi/proxy/plugin_dispatcher.cc
index 37f1f1fbddc605a2bd575a76bdae9daf6a1e879f..70f9cfb50256cdbd4291696dac80c2dbbd747f93 100644
--- a/ppapi/proxy/plugin_dispatcher.cc
+++ b/ppapi/proxy/plugin_dispatcher.cc
@@ -339,8 +339,9 @@ void PluginDispatcher::LockedDispatchResourceReply(
   Resource* resource = PpapiGlobals::Get()->GetResourceTracker()->GetResource(
       reply_params.pp_resource());
   if (!resource) {
-    if (reply_params.sequence())
-      NOTREACHED();
+    DLOG_IF(INFO, reply_params.sequence() != 0)
+        << "Pepper resource reply message received but the resource doesn't "
+           "exist (probably has been destroyed).";
     return;
   }
   resource->OnReplyReceived(reply_params, nested_msg);