Add GetWakeLockWithoutContext() in WakeLockContextProvider mojo interface.

device/wake_lock/public/interfaces/wake_lock_context_provider.mojom

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module device.mojom;
 
 import "device/wake_lock/public/interfaces/wake_lock_context.mojom";
 
 interface WakeLockContextProvider {
 
   // Gets a WakeLockContext that is associated with |context_id|. |context_id|
   // 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.

 };