Add GetWakeLockWithoutContext() in WakeLockContextProvider mojo interface.

device/wake_lock/wake_lock_service_impl.cc

Index: device/wake_lock/wake_lock_service_impl.cc
diff --git a/device/wake_lock/wake_lock_service_impl.cc b/device/wake_lock/wake_lock_service_impl.cc
index f5ca821d762bfd2f23240bc8aa5a54a9a4024acd..fcf4660806abe7b82cc0611d39bae21aa1b6857f 100644
--- a/device/wake_lock/wake_lock_service_impl.cc
+++ b/device/wake_lock/wake_lock_service_impl.cc
@@ -133,6 +133,9 @@ void WakeLockServiceImpl::CreateWakeLock() {
     return;
 
 #if defined(OS_ANDROID)
+  if (context_id_ == WakeLockServiceContext::WakeLockInvalidContextId)
+    return;

[blundell, 2017/05/12 12:42:18]

Maybe we should LOG(ERROR) here, as if the client is using a wake lock to
prevent display sleep on Android and isn't passing a context ID, they're quite
likely not getting the behavior they want.

[ke.he, 2017/05/12 16:09:38]

Done.

+
   gfx::NativeView native_view = native_view_getter_.Run(context_id_);
   if (native_view)
     wake_lock_.get()->InitDisplaySleepBlocker(native_view);