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 6b7e86e149b0f99c23ad80ec0719656f98bf6f43..71d01993a9163c05dd91efc3fbef81a1beb4c089 100644
--- a/media/mojo/interfaces/media_renderer.mojom
+++ b/media/mojo/interfaces/media_renderer.mojom
@@ -28,6 +28,10 @@ interface MediaRenderer {
 
   // Sets the output volume. The default volume should be 1.
   SetVolume(float volume);
+
+  // Sets the CDM to be used by the renderer. Returns whether the CDM is
+  // successfully attached.
+  SetCdm(int32 cdm_id) => (bool success);
 };
 
 interface MediaRendererClient {