Update the name of the MediaDevicesListener mojo interface name

A previous CL that moved some of the functionality to Blink missed this,
which prevents firing of the devicechange event.

Bug: 794177
Change-Id: I5ab74f5605979ec508c0620d75eb41585b32f218
Reviewed-on: https://chromium-review.googlesource.com/822259Reviewed-by: Chandan Padhi <c.padhi@samsung.com>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523500}

content/public/app/mojo/content_renderer_manifest.json

@@ -46,12 +46,12 @@
           "blink::mojom::EngagementClient",
           "blink::mojom::InstallationService",
           "blink::mojom::ManifestManager",
+          "blink::mojom::MediaDevicesListener",
           "blink::mojom::TextSuggestionBackend",
           "content::mojom::ImageDownloader",
           "content::mojom::FrameInputHandler",
           "content::mojom::MediaStreamDispatcher",
-          "content::mojom::Widget",
-          "mojom::MediaDevicesListener"
+          "content::mojom::Widget"
         ]
       },
       "requires": {