media: Remove enable_test_mojo_media_client gn arg

It's currently set to false by default and there's no bot setting it.
It was used in manual testing but hasn't been used for a long time.
This CL removes this gn arg.

Bug: 1067786
Change-Id: Idf7c57898f335b10441eb32e1509b2bee25c5368
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2136310Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756498}

media/media_options.gni

@@ -168,10 +168,6 @@ declare_args() {
       (is_android || is_chromeos || is_mac || is_win || enable_library_cdms ||
        (is_desktop_linux && use_vaapi) || is_chromecast)
 
-  # Enable the TestMojoMediaClient to be used in mojo MediaService. This is for
-  # testing only and will override the default platform MojoMediaClient, if any.
-  enable_test_mojo_media_client = false
-
   # When enabled, this feature allows developers to use a runtime flag to
   # choose the implementation of the renderer that is used. On a build which
   # enables the mojo renderer, if --disable-mojo-renderer is passed at start-up,

media/mojo/BUILD.gn

@@ -21,7 +21,6 @@ buildflag_header("buildflags") {
   if (!enable_mojo_media) {
     assert(mojo_media_services == [], "Mojo media is not enabled")
     assert(mojo_media_host == "none", "Mojo media is not enabled")
-    assert(!enable_test_mojo_media_client, "Mojo media is not enabled")
   } else {
     assert(mojo_media_services != [], "No mojo media service specified")
     foreach(service, mojo_media_services) {
@@ -52,7 +51,6 @@ buildflag_header("buildflags") {
   flags = [
     "ENABLE_CAST_RENDERER=$enable_cast_renderer",
     "ENABLE_MOJO_MEDIA=$enable_mojo_media",
-    "ENABLE_TEST_MOJO_MEDIA_CLIENT=$enable_test_mojo_media_client",
     "ENABLE_MOJO_RENDERER=$enable_mojo_renderer",
     "ENABLE_MOJO_CDM=$enable_mojo_cdm",
     "ENABLE_MOJO_AUDIO_DECODER=$enable_mojo_audio_decoder",

media/mojo/services/media_service_factory.cc

@@ -7,6 +7,7 @@
 #include <memory>
 
 #include "base/logging.h"
+#include "build/build_config.h"
 #include "media/mojo/buildflags.h"
 #include "media/mojo/services/gpu_mojo_media_client.h"
 #include "media/mojo/services/media_service.h"
@@ -20,9 +21,7 @@ namespace media {
 
 std::unique_ptr<MediaService> CreateMediaService(
     mojo::PendingReceiver<mojom::MediaService> receiver) {
-#if BUILDFLAG(ENABLE_TEST_MOJO_MEDIA_CLIENT)
-  return CreateMediaServiceForTesting(std::move(receiver));
-#elif defined(OS_ANDROID)
+#if defined(OS_ANDROID)
   return std::make_unique<MediaService>(
       std::make_unique<AndroidMojoMediaClient>(), std::move(receiver));
 #else

media/mojo/services/media_service_factory.h

@@ -29,8 +29,7 @@ namespace media {
 class MediaGpuChannelManager;
 
 // Creates a MediaService instance using the default MojoMediaClient on each
-// platform. Uses the TestMojoMediaClient if |enable_test_mojo_media_client| is
-// true.
+// platform.
 std::unique_ptr<MediaService> MEDIA_MOJO_EXPORT
 CreateMediaService(mojo::PendingReceiver<mojom::MediaService> receiver);