media: Support creation and SetCdm() for mojo based CDM.

media/mojo/interfaces/media_renderer.mojom

Index: media/mojo/interfaces/media_renderer.mojom
diff --git a/media/mojo/interfaces/media_renderer.mojom b/media/mojo/interfaces/media_renderer.mojom
index 9165a338cd80b8249bbe782b1a9322c1f868ab46..8fd40e692afe4534c8773ed4822eb05e64f4a53e 100644
--- a/media/mojo/interfaces/media_renderer.mojom
+++ b/media/mojo/interfaces/media_renderer.mojom
@@ -29,6 +29,10 @@ interface MediaRenderer {
 
   // Sets the output volume. The default volume should be 1.
   SetVolume(float volume);
+
+  // Attaches the CDM associated with |cdm_id| to the renderer service,
+  // executing the callback with whether the CDM was successfully attached.
+  SetCdm(int32 cdm_id) => (bool success);
 };
 
 interface MediaRendererClient {