Change the cpp wrappers of audio input/video capture to use CompletionCallbackWithOutput.

ppapi/examples/audio_input/audio_input.cc

Index: ppapi/examples/audio_input/audio_input.cc
diff --git a/ppapi/examples/audio_input/audio_input.cc b/ppapi/examples/audio_input/audio_input.cc
index 7d156b72e6381d00b6fcde660edc262a66c6507c..62bf2995cc86a8d7544a2068bdb6054f8f6f99b3 100644
--- a/ppapi/examples/audio_input/audio_input.cc
+++ b/ppapi/examples/audio_input/audio_input.cc
@@ -93,9 +93,10 @@ class MyInstance : public pp::Instance {
     if (message_data.is_string()) {
       std::string event = message_data.AsString();
       if (event == "PageInitialized") {
-        pp::CompletionCallback callback = callback_factory_.NewCallback(
-            &MyInstance::EnumerateDevicesFinished);
-        int32_t result = audio_input_.EnumerateDevices(&devices_, callback);
+        pp::CompletionCallbackWithOutput<std::vector<pp::DeviceRef_Dev> >
+            callback = callback_factory_.NewCallbackWithOutput(
+                &MyInstance::EnumerateDevicesFinished);
+        int32_t result = audio_input_.EnumerateDevices(callback);
         if (result != PP_OK_COMPLETIONPENDING)
           PostMessage(pp::Var("EnumerationFailed"));
       } else if (event == "UseDefault") {
@@ -241,10 +242,12 @@ class MyInstance : public pp::Instance {
     }
   }
 
-  void EnumerateDevicesFinished(int32_t result) {
+  void EnumerateDevicesFinished(int32_t result,
+                                std::vector<pp::DeviceRef_Dev>& devices) {
     static const char* const kDelimiter = "#__#";
 
     if (result == PP_OK) {
+      devices_.swap(devices);
       std::string device_names;
       for (size_t index = 0; index < devices_.size(); ++index) {
         pp::Var name = devices_[index].GetName();