Rename InterfaceID to ApiID and move the file.

This was originally in the proxy and had a 1:1 correspondence with an
interface. Then we reused this for other stuff and then merged some interfaces
into larger APIs (ppapi/thunk/*_api.h) so the name was no longer accurate.
It was wrong to be in the proxy directory since directories at a "lower level"
than the proxy (ppapi/shared_impl and webkit/plugins/ppapi) depended on it.

This renames to ApiID (I avoided APIID since it looks like a define) which is
the proper description of the class, and moved it to shared_impl. This fixes
the deps since there are no longer any bad dependencies on the proxy directory.

TEST=it compiles
BUG=none

Review URL: http://codereview.chromium.org/8333004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@106619 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/ppapi/proxy/ppb_audio_proxy.h b/ppapi/proxy/ppb_audio_proxy.h
index b548e7237..feee8dc 100644
--- a/ppapi/proxy/ppb_audio_proxy.h
+++ b/ppapi/proxy/ppb_audio_proxy.h
@@ -43,7 +43,7 @@
   // InterfaceProxy implementation.
   virtual bool OnMessageReceived(const IPC::Message& msg);
 
-  static const InterfaceID kInterfaceID = INTERFACE_ID_PPB_AUDIO;
+  static const ApiID kApiID = API_ID_PPB_AUDIO;
 
  private:
   // Plugin->renderer message handlers.