Device Service: Decouple Wake Lock from //content

device/wake_lock/public/interfaces/README.md

+Provides the ability to block the device / display from sleeping.
+
+On Android, the implementation is inherently coupled to the NativeView
+associated with the context of the requestor due to system APIs. To handle
+this coupling, the Wake Lock usage model on Android is as follows:
+
+(1) The embedder passes in a callback at Device Service construction that
+enables the Wake Lock implementation to map (embedder-specific) context IDs to
+NativeViews.
+(2) For a given embedder-specific context, a trusted client
+connects to the WakeLockContextProvider interface and gets a
+WakeLockContext instance that is associated with that context.
+(3) That trusted client then forwards requests to bind wake locks from
+untrusted clients that are made within that context, with the Wake Lock
+implementation using the callback from (1) as necessary to obtain the
+NativeView associated with that context.
+
+On other platforms, the usage model is similar but the callback is not
+necessary/employed.