Use OnceCallback on Mojo interfaces in //device/geolocation

This CL flips `use_once_calback` flag on the Mojo code generator, and
fixes all compile errors after it. After this CL, Mojo interfaces in
//device/geolocation starts using base::OnceCallback instead of
base::Callback on its return value handling.

The migration recipe was:
 - Convert pass-by-ref callback objects to pass-by-value.
 - Use std::move() to forward it to other consumer, or to invoke it
   with Callback::Run().
 - Handle wherever copies are required manually.
 - Check if the conversion doesn't change the semantics. As the transfer
   and invocation clobber the callback object, care about use-after-move.
   It's considered safe to consume almost scoped-out callback.

BUG=714018

Review-Url: https://codereview.chromium.org/2866003002
Cr-Commit-Position: refs/heads/master@{#475807}

device/geolocation/geolocation_service_impl.cc

@@ -118,14 +118,14 @@ void GeolocationServiceImpl::SetHighAccuracy(bool high_accuracy) {
 }
 
 void GeolocationServiceImpl::QueryNextPosition(
-    const QueryNextPositionCallback& callback) {
+    QueryNextPositionCallback callback) {
   if (!position_callback_.is_null()) {
     DVLOG(1) << "Overlapped call to QueryNextPosition!";
     OnConnectionError();  // Simulate a connection error.
     return;
   }
 
-  position_callback_ = callback;
+  position_callback_ = std::move(callback);
 
   if (has_position_to_report_)
     ReportCurrentPosition();
@@ -178,8 +178,7 @@ void GeolocationServiceImpl::OnLocationUpdate(const Geoposition& position) {
 }
 
 void GeolocationServiceImpl::ReportCurrentPosition() {
-  position_callback_.Run(current_position_.Clone());
-  position_callback_.Reset();
+  std::move(position_callback_).Run(current_position_.Clone());
   has_position_to_report_ = false;
 }
 

device/geolocation/geolocation_service_impl.h

@@ -42,7 +42,7 @@ class GeolocationServiceImpl : public mojom::GeolocationService {
  private:
   // mojom::GeolocationService:
   void SetHighAccuracy(bool high_accuracy) override;
-  void QueryNextPosition(const QueryNextPositionCallback& callback) override;
+  void QueryNextPosition(QueryNextPositionCallback callback) override;
 
   void OnConnectionError();
 

device/geolocation/public/interfaces/BUILD.gn

@@ -9,9 +9,6 @@ mojom("interfaces") {
     "geolocation.mojom",
   ]
 
-  # TODO(crbug.com/714018): Convert the implementation to use OnceCallback.
-  use_once_callback = false
-
   # TODO(crbug.com/699569): Convert to use the new JS bindings.
   use_new_js_bindings = false
 }