MockAudioEncoder: Use a dedicated marker method for test expectations

This makes the sequence of expected calls easier to read. Also, we can
save one line and get rid of a gmock warning by expecting the
MockAudioEncoder object to be destroyed at the end of the test instead
of making a final marker call.

Review URL: https://codereview.webrtc.org/1331793003

Cr-Commit-Position: refs/heads/master@{#9916}
diff --git a/webrtc/modules/audio_coding/codecs/mock/mock_audio_encoder.h b/webrtc/modules/audio_coding/codecs/mock/mock_audio_encoder.h
index a34edb3..95426d8 100644
--- a/webrtc/modules/audio_coding/codecs/mock/mock_audio_encoder.h
+++ b/webrtc/modules/audio_coding/codecs/mock/mock_audio_encoder.h
@@ -21,6 +21,7 @@
  public:
   ~MockAudioEncoder() override { Die(); }
   MOCK_METHOD0(Die, void());
+  MOCK_METHOD1(Mark, void(std::string desc));
   MOCK_CONST_METHOD0(MaxEncodedBytes, size_t());
   MOCK_CONST_METHOD0(SampleRateHz, int());
   MOCK_CONST_METHOD0(NumChannels, int());
diff --git a/webrtc/modules/audio_coding/main/acm2/codec_owner_unittest.cc b/webrtc/modules/audio_coding/main/acm2/codec_owner_unittest.cc
index 0c510c0..ec1bb0d 100644
--- a/webrtc/modules/audio_coding/main/acm2/codec_owner_unittest.cc
+++ b/webrtc/modules/audio_coding/main/acm2/codec_owner_unittest.cc
@@ -115,19 +115,19 @@
     EXPECT_CALL(external_encoder,
                 EncodeInternal(0, audio, arraysize(encoded), encoded))
         .WillOnce(Return(info));
-    EXPECT_CALL(external_encoder, Reset());
-    EXPECT_CALL(external_encoder, Reset());
+    EXPECT_CALL(external_encoder, Mark("A"));
+    EXPECT_CALL(external_encoder, Mark("B"));
     info.encoded_timestamp = 2;
     EXPECT_CALL(external_encoder,
                 EncodeInternal(2, audio, arraysize(encoded), encoded))
         .WillOnce(Return(info));
-    EXPECT_CALL(external_encoder, Reset());
+    EXPECT_CALL(external_encoder, Die());
   }
 
   info = codec_owner_.Encoder()->Encode(0, audio, arraysize(audio),
                                         arraysize(encoded), encoded);
   EXPECT_EQ(0u, info.encoded_timestamp);
-  external_encoder.Reset();  // Dummy call to mark the sequence of expectations.
+  external_encoder.Mark("A");
 
   // Change to internal encoder.
   CodecInst codec_inst = kDefaultCodecInst;
@@ -136,14 +136,13 @@
   // Don't expect any more calls to the external encoder.
   info = codec_owner_.Encoder()->Encode(1, audio, arraysize(audio),
                                         arraysize(encoded), encoded);
-  external_encoder.Reset();  // Dummy call to mark the sequence of expectations.
+  external_encoder.Mark("B");
 
   // Change back to external encoder again.
   codec_owner_.SetEncoders(&external_encoder, -1, VADNormal, -1);
   info = codec_owner_.Encoder()->Encode(2, audio, arraysize(audio),
                                         arraysize(encoded), encoded);
   EXPECT_EQ(2u, info.encoded_timestamp);
-  external_encoder.Reset();  // Dummy call to mark the sequence of expectations.
 }
 
 }  // namespace acm2