Remove ChangeUniqueID.

This fixes a two year old TODO of deleting dead code :)
In cases where the _id or id_ member variable is being used for tracing,
I changed the member to at least be const.

It doesn't look like id's are that useful anymore so maybe the next step is to get rid of them.

BUG=
R=henrika@webrtc.org, perkj@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/37849004

Cr-Commit-Position: refs/heads/master@{#8201}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8201 4adac7df-926f-26a2-2b94-8c16560cd09d

talk/app/webrtc/test/fakeaudiocapturemodule.cc

@@ -112,11 +112,6 @@ int32_t FakeAudioCaptureModule::Process() {
   return 0;
 }
 
-int32_t FakeAudioCaptureModule::ChangeUniqueId(const int32_t /*id*/) {
-  ASSERT(false);
-  return 0;
-}
-
 int32_t FakeAudioCaptureModule::ActiveAudioLayer(
     AudioLayer* /*audio_layer*/) const {
   ASSERT(false);

talk/app/webrtc/test/fakeaudiocapturemodule.h

@@ -78,7 +78,6 @@ class FakeAudioCaptureModule
   // PeerConnection an assertion is triggered if it is in fact called.
   virtual int64_t TimeUntilNextProcess() OVERRIDE;
   virtual int32_t Process() OVERRIDE;
-  virtual int32_t ChangeUniqueId(const int32_t id) OVERRIDE;
 
   virtual int32_t ActiveAudioLayer(AudioLayer* audio_layer) const OVERRIDE;