Partially convert geolocation IPC to Mojo.

content/common/geolocation_service.mojom

+// Copyright 2014 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.
+
+import "content/public/common/mojo_geoposition.mojom"
+
+module content {
+
+// The Geolocation service provides updates on the device's location to its
+// client. It starts providing updates once |StartUpdating()| is called and
+// continues until the connection is closed. |StartUpdating()| can be called
+// multiple times to change the accuracy with which the location is being
+// tracked.
+[Client=GeolocationServiceClient]
+interface GeolocationService {
+  StartUpdating(bool high_accuracy);
+};

[Tom Sepez, 2014/10/21 18:10:06]

Nit: are you sure you don't want to spec a StopUpdating() method while we're at
it even if its not being used at the moment?  Closing the pipe to accomplish
this feels kinda heavy handed to me.

[blundell, 2014/10/21 20:17:41]

Originally I wanted the client connecting to the service implicitly being a
request to start updating, and the connection being dropped being the way to
stop updating. I had to add the StartUpdating() method because of the
|high_accuracy| parameter and the fact that there's no way for a client to pass
params that a service should be constructed with when connecting to that
service.

I don't have a strong preference here but closing the pipe when updates should
stop feels more idiomatic to me in the Mojo world than adding a StopUpdating()
method. Would be happy to get a Mojo owner's opinion on the question.

[Aaron Boodman, 2014/10/22 00:25:38]

Drive-by: I agree that dropping the pipe is more idiomatic mojo.

As to StartUpdate().... is it possible to have a EnableHighAccuracy(bool) method
instead which changes whether the current service is in "high-accuracy mode" or
not?

Not a big deal, just inches closer to what you wanted the interface to be
originally.

+
+interface GeolocationServiceClient {
+  OnLocationUpdate(MojoGeoposition geoposition);
+};
+
+}