Move ownership of PowerSaveBlocker from WakeLockServiceContext to WakeLockServiceImpl

device/wake_lock/public/interfaces/wake_lock_service.mojom

Index: device/wake_lock/public/interfaces/wake_lock_service.mojom
diff --git a/device/wake_lock/public/interfaces/wake_lock_service.mojom b/device/wake_lock/public/interfaces/wake_lock_service.mojom
index 8c6e7a494c0f32fd97537713ab2222585860d65f..d5a8c123e84ac0a9e09d3956c8139cb4bd261994 100644
--- a/device/wake_lock/public/interfaces/wake_lock_service.mojom
+++ b/device/wake_lock/public/interfaces/wake_lock_service.mojom
@@ -8,4 +8,10 @@ module device.mojom;
 interface WakeLockService {
   RequestWakeLock();
   CancelWakeLock();
+
+  // TODO(heke): The AddClient() interface is only used by WebContents for the

[blundell, 2017/05/02 11:27:43]

Actually, I think it's fine to leave this method on this interface. There is a
use case for coalescing requests from multiple clients. In the future, maybe
there will be clients other than Blink for that use case.

[ke.he, 2017/05/04 11:54:14]

Yes, Totally understand after the mail discussion.

+  // purpose of coalescing requests from frames. It is better to split it into
+  // a seperate mojo interface and refactor WakeLockServiceContext and
+  // WakeLockServiceImpl accordingly.
+  AddClient(WakeLockService& wake_lock);
 };