Refactor rtc_unittests into several targets.

webrtc/sdk/objc/Framework/UnitTests/avformatmappertests.mm

 /*
  *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 142 matching lines @@
 
   // valid media subtype, valid framerate
   AVCaptureDeviceFormatMock* mock = [AVCaptureDeviceFormatMock validFormat];
   [[[mockDevice stub] andReturn:@[ mock ]] formats];
 
   // when
   std::set<cricket::VideoFormat> result =
       webrtc::GetSupportedVideoFormatsForDevice(mockDevice);
 
   // then
-  EXPECT_EQ(1, result.size());
+  EXPECT_EQ(1u, result.size());
 
   // make sure the set has the expected format
   EXPECT_EQ(expectedFormat, *result.begin());
 }
 
 TEST(AVFormatMapperTest, MediaSubtypePreference) {
   // given
   id mockDevice = [OCMockObject mockForClass:[AVCaptureDevice class]];
 
   // valid media subtype, valid framerate
@@ skipping 60 matching lines @@
   [[mockDevice expect] unlockForConfiguration];
 
   // when
   bool resultFormat = webrtc::SetFormatForCaptureDevice(mockDevice, nil,
                                                         cricket::VideoFormat());
 
   // then
   EXPECT_FALSE(resultFormat);
   [mockDevice verify];
 }