Restore sample_rate_hz() until Chromium is updated to not use it.

TBR=bjornv
TESTED=Chromium builds against webrtc head.
BUG=2894

Review URL: https://webrtc-codereview.appspot.com/12349004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5962 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_processing/include/mock_audio_processing.h

@@ -194,6 +194,8 @@ class MockAudioProcessing : public AudioProcessing {
       int(int rate));
   MOCK_CONST_METHOD0(input_sample_rate_hz,
       int());
+  MOCK_CONST_METHOD0(sample_rate_hz,
+      int());
   MOCK_CONST_METHOD0(proc_sample_rate_hz,
       int());
   MOCK_CONST_METHOD0(proc_split_sample_rate_hz,