Adds GeolocationFeature for Blimp Geolocation project.

blimp/client/feature/geolocation_feature.h

Index: blimp/client/feature/geolocation_feature.h
diff --git a/blimp/client/feature/geolocation_feature.h b/blimp/client/feature/geolocation_feature.h
new file mode 100644
index 0000000000000000000000000000000000000000..8bb9b25c3756b4e58ba15e68768a5f5308cbd299
--- /dev/null
+++ b/blimp/client/feature/geolocation_feature.h
@@ -0,0 +1,66 @@
+// Copyright 2016 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.
+
+#ifndef BLIMP_CLIENT_FEATURE_GEOLOCATION_FEATURE_H_
+#define BLIMP_CLIENT_FEATURE_GEOLOCATION_FEATURE_H_
+
+#include <memory>
+#include <string>
+
+#include "blimp/common/proto/geolocation.pb.h"
+#include "blimp/net/blimp_message_processor.h"
+#include "device/geolocation/geoposition.h"
+#include "device/geolocation/location_provider.h"
+
+namespace blimp {
+namespace client {
+
+// Client-side feature handling geolocation messages.
+class GeolocationFeature : public BlimpMessageProcessor {
+ public:
+  explicit GeolocationFeature(
+      std::unique_ptr<device::LocationProvider> location_provider);

[Wez, 2016/08/02 01:18:11]

nit: Add a comment to explain how |location_provider| is used, e.g. to make
clear that it is the _only_ LocationProvider that this class will consider -
this class won't e.g. create "network" location providers to gather backup
information from.

[CJ, 2016/08/03 20:06:03]

Done.

+  ~GeolocationFeature() override;
+
+  // Sets the BlimpMessageProcessor that will be used to send
+  // BlimpMessage::GEOLOCATION messages to the engine.
+  void set_outgoing_message_processor(
+      std::unique_ptr<BlimpMessageProcessor> processor);
+
+  // BlimpMessageProcessor implementation.
+  void ProcessMessage(std::unique_ptr<BlimpMessage> message,
+                      const net::CompletionCallback& callback) override;
+
+ private:
+  // Sends engine an update of the client's geoposition.
+  void OnLocationUpdate(const device::LocationProvider* location_provider,
+                        const device::Geoposition& position);
+
+  // Communicates to the client a change of interest level from the engine.
+  void OnGeolocationInterestUpdate(

[Wez, 2016/08/02 01:18:11]

nit: It's a little strange to have two On*() methods but going in different
directions - this one is really about *handling* an incoming InterestUpdate
message, right? So consider calling it HandleSetInterestLevelMessage, or simply
SetInterestLevel.

[CJ, 2016/08/03 20:06:03]

Done.

+          GeolocationSetInterestLevelMessage::Level level);
+
+  // Creates a GeolocationPositionMessage that reflects the given
+  // geoposition and sends it to the engine.
+  void SendGeolocationPositionMessage(const device::Geoposition& position);
+
+  // Creates a GeolocationErrorMessage that reflects the error defined
+  // in the given geoposition and sends it.
+  void SendGeolocationErrorMessage(
+      const device::Geoposition::ErrorCode& error_code,
+      const std::string& error_message);
+
+  // Used to obtain the client's location.
+  std::unique_ptr<device::LocationProvider> location_provider_;
+
+  // Used to send BlimpMessage::GEOLOCATION message to the engine.
+  std::unique_ptr<BlimpMessageProcessor> outgoing_message_processor_;
+
+  DISALLOW_COPY_AND_ASSIGN(GeolocationFeature);
+};
+
+}  // namespace client
+}  // namespace blimp
+
+#endif  // BLIMP_CLIENT_FEATURE_GEOLOCATION_FEATURE_H_