Remove AudioDeviceObserver and make ADM not inherit from the Module interface.

pc/test/fakeaudiocapturemodule_unittest.cc

Index: pc/test/fakeaudiocapturemodule_unittest.cc
diff --git a/pc/test/fakeaudiocapturemodule_unittest.cc b/pc/test/fakeaudiocapturemodule_unittest.cc
index 312c4e8f969c3078864ff67e78031b76aaa3ea3a..0e7574f4c64a593334435d59ad3ac3c91051aa3d 100644
--- a/pc/test/fakeaudiocapturemodule_unittest.cc
+++ b/pc/test/fakeaudiocapturemodule_unittest.cc
@@ -133,14 +133,6 @@ class FakeAdmTest : public testing::Test,
   size_t rec_buffer_bytes_;
 };
 
-TEST_F(FakeAdmTest, TestProcess) {
-  // Next process call must be some time in the future (or now).
-  EXPECT_LE(0, fake_audio_capture_module_->TimeUntilNextProcess());
-  // Process call updates TimeUntilNextProcess() but there are no guarantees on
-  // timing so just check that Process can be called successfully.
-  fake_audio_capture_module_->Process();
-}
-
 TEST_F(FakeAdmTest, PlayoutTest) {
   EXPECT_EQ(0, fake_audio_capture_module_->RegisterAudioCallback(this));