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

ppapi/shared_impl/ppb_device_ref_shared.h

Index: ppapi/shared_impl/ppb_device_ref_shared.h
diff --git a/ppapi/shared_impl/ppb_device_ref_shared.h b/ppapi/shared_impl/ppb_device_ref_shared.h
index 895baa5d26d2e5960e43f89c307d111bf5c63c52..9ea367ee05d336667dc1cdb6136974d1afd1cc73 100644
--- a/ppapi/shared_impl/ppb_device_ref_shared.h
+++ b/ppapi/shared_impl/ppb_device_ref_shared.h
@@ -21,6 +21,12 @@ namespace ppapi {
 struct PPAPI_SHARED_EXPORT DeviceRefData {
   DeviceRefData();
 
+  bool operator==(const DeviceRefData& other) const {
+    return type == other.type &&
+           name == other.name &&
+           id == other.id;
+  }
+
   PP_DeviceType_Dev type;
   std::string name;
   std::string id;