[Chromecast] Hook up mojo media pipeline.

content/browser/BUILD.gn

Index: content/browser/BUILD.gn
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index 426bc69dc337d4ff3ab8bd80375068db1d2253ae..3be09067aaa70dd4ef8d6f13a26a3804273d6ac5 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -520,14 +520,6 @@ source_set("browser") {
     deps += [ "//third_party/boringssl" ]
   }
 
-  if (enable_mojo_media != "none") {

[alokp, 2016/02/02 00:40:44]

I had to make this change to not link the default mojo media application to all
content embedders. It should have been done as part of this patch:
https://codereview.chromium.org/1544853003/

This has been moved to chrome/browser/BUILD.gn. I expected to add a similar
dependency to content/shell/browser, but surprisingly I did not get any link
error when building content_shell with enable_mojo_media="browser". In fact I
discovered that I do not need any of the deps in utility and gpu. I successfully
compiled both chrome and content_shell with various enable_mojo_media configs.

Since you added these deps in the first place, can you tell me what/how I should
build to trigger the need for these deps?

[xhwang, 2016/02/02 00:50:12]

When the target is dependent on the "applicaiton", it'll also expose the
"enable_mojo_media_config" [1], which will define
ENABLE_MOJO_MEDIA_IN_GPU_PROCESS etc [2].

Now you removed the dependency, ENABLE_MOJO_MEDIA_IN_GPU_PROCESS will not be
defined at all. That's how [3] still compiles (I think). But when you try to
connect to the service there will be a connection error.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/media/mojo/service...

[2]
https://code.google.com/p/chromium/codesearch#chromium/src/media/mojo/service...

[3]
https://code.google.com/p/chromium/codesearch#chromium/src/content/gpu/gpu_pr...

-    configs += [ "//media/mojo/services:enable_mojo_media_config" ]
-  }
-
-  if (enable_mojo_media == "browser") {
-    deps += [ "//media/mojo/services:application" ]
-  }
-
   if (enable_webvr) {
     sources += [
       "vr/vr_device.cc",