[Chromecast] Upgrade to new CMA backend API

chromecast/media/cma/backend/BUILD.gn

Index: chromecast/media/cma/backend/BUILD.gn
diff --git a/chromecast/media/cma/backend/BUILD.gn b/chromecast/media/cma/backend/BUILD.gn
index 7507b7d6ea0e7c6c6d90e303e58e1da6186a30bb..57f67ae720e87347d60ce585f445e1594e736d2b 100644
--- a/chromecast/media/cma/backend/BUILD.gn
+++ b/chromecast/media/cma/backend/BUILD.gn
@@ -4,22 +4,8 @@
 
 source_set("backend") {
   sources = [
-    "audio_pipeline_device_default.cc",
-    "audio_pipeline_device_default.h",
-    "media_clock_device_default.cc",
-    "media_clock_device_default.h",
-    "media_component_device_default.cc",
-    "media_component_device_default.h",
     "media_pipeline_backend_default.cc",
     "media_pipeline_backend_default.h",
-    "video_pipeline_device_default.cc",
-    "video_pipeline_device_default.h",
-  ]
-
-  # This target cannot depend on //media. Include these headers directly.
-  sources += [
-    "//media/base/media_export.h",
-    "//media/base/timestamp_constants.h",
   ]
 
   public_deps = [