Add GetWakeLockWithoutContext() in WakeLockContextProvider mojo interface.

device/wake_lock/public/interfaces/wake_lock_context_provider.mojom

Index: device/wake_lock/public/interfaces/wake_lock_context_provider.mojom
diff --git a/device/wake_lock/public/interfaces/wake_lock_context_provider.mojom b/device/wake_lock/public/interfaces/wake_lock_context_provider.mojom
index b8f1c8f6ffc2c0fb86f756348b3bccab74c37d93..d1dc7a168d9c1de63a4973362fff1ed0fc0be42a 100644
--- a/device/wake_lock/public/interfaces/wake_lock_context_provider.mojom
+++ b/device/wake_lock/public/interfaces/wake_lock_context_provider.mojom
@@ -12,4 +12,7 @@ interface WakeLockContextProvider {
   // is used to obtain the NativeView associated with the relevant context on
   // Android (see WakeLockContextCallback).

[blundell, 2017/05/11 15:42:40]

Let's note that context_ids must be >=0, and DCHECK that in the impl.

[ke.he, 2017/05/12 12:24:24]

Done.

   GetWakeLockContextForID(int32 context_id, WakeLockContext& context);
+
+  // Gets a WakeLockContext that is not associated with any |context_id|.
+  GetUnassociatedWakeLockContext(WakeLockContext& context);

[blundell, 2017/05/11 15:42:40]

Looking at the client usage, I now think that it would be better for this method
to be:

GetWakeLockWithoutContext(type, reason, description, WakeLockService&
wake_lock);

That way clients won't need to go through the dance of getting a context first.

Let's add to the comment here:

// Gets a Wake Lock outside of any context. This method can be used // if the
client does not have any context available (e.g., is not // within the context
of a WebContents). However, note that the resulting
// Wake Lock will not have any effect on Android.

[ke.he, 2017/05/11 16:08:05]

Thanks. I will update them tomorrow :D

In this way this interface provides both WakeLockContext and WakeLockService. I
feel maybe we need to change the interface name "context_provider" too ?

[ke.he, 2017/05/12 12:24:24]

Done.

 };