Added MediaSourceState unit test.

media/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/buildflag_header.gni")
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/features.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//build/config/ui.gni")
@@ skipping 527 matching lines @@
     "filters/decrypting_video_decoder_unittest.cc",
     "filters/fake_video_decoder.cc",
     "filters/fake_video_decoder.h",
     "filters/fake_video_decoder_unittest.cc",
     "filters/file_data_source_unittest.cc",
     "filters/frame_processor_unittest.cc",
     "filters/h264_bit_reader_unittest.cc",
     "filters/h264_parser_unittest.cc",
     "filters/ivf_parser_unittest.cc",
     "filters/jpeg_parser_unittest.cc",
+    "filters/media_source_state_unittest.cc",
     "filters/memory_data_source_unittest.cc",
     "filters/pipeline_controller_unittest.cc",
     "filters/source_buffer_stream_unittest.cc",
     "filters/video_cadence_estimator_unittest.cc",
     "filters/video_decoder_selector_unittest.cc",
     "filters/video_frame_stream_unittest.cc",
     "filters/video_renderer_algorithm_unittest.cc",
     "filters/vp8_bool_decoder_unittest.cc",
     "filters/vp8_parser_unittest.cc",
     "filters/vp9_parser_unittest.cc",
@@ skipping 341 matching lines @@
 fuzzer_test("media_webm_muxer_fuzzer") {
   sources = [
     "muxers/webm_muxer_fuzzertest.cc",
   ]
   deps = [
     ":media",
     "//base",
     "//third_party/libwebm",
   ]
 }