Define MockFrameTransformer in test/.

Add MockFrameTransformer to test/, and remove definitions from unit test
files.

Bug: webrtc:11380
Change-Id: Ia709883e8d000852e3f71e7bfb87877072e22aeb
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/174001
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Marina Ciocea <marinaciocea@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31151}
diff --git a/call/rtp_video_sender_unittest.cc b/call/rtp_video_sender_unittest.cc
index d7d7034..20c6b54 100644
--- a/call/rtp_video_sender_unittest.cc
+++ b/call/rtp_video_sender_unittest.cc
@@ -26,6 +26,7 @@
 #include "test/field_trial.h"
 #include "test/gmock.h"
 #include "test/gtest.h"
+#include "test/mock_frame_transformer.h"
 #include "test/mock_transport.h"
 #include "test/scenario/scenario.h"
 #include "test/time_controller/simulated_time_controller.h"
@@ -825,17 +826,6 @@
 }
 
 TEST(RtpVideoSenderTest, SimulcastSenderRegistersFrameTransformers) {
-  class MockFrameTransformer : public FrameTransformerInterface {
-   public:
-    MOCK_METHOD3(TransformFrame,
-                 void(std::unique_ptr<video_coding::EncodedFrame> frame,
-                      std::vector<uint8_t> additional_data,
-                      uint32_t ssrc));
-    MOCK_METHOD2(RegisterTransformedFrameSinkCallback,
-                 void(rtc::scoped_refptr<TransformedFrameCallback>, uint32_t));
-    MOCK_METHOD1(UnregisterTransformedFrameSinkCallback, void(uint32_t));
-  };
-
   rtc::scoped_refptr<MockFrameTransformer> transformer =
       new rtc::RefCountedObject<MockFrameTransformer>();