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 616e6770f72122c1c66fc133ca1f2affe94120a3..cbf558f176f7dd4589157e55c0895df2d2c32d23 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 {