Geolocation: extract ContentBrowserClient methods specific to Geolocation into a class

content/public/browser/geolocation_provider.h

 // Copyright (c) 2012 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 CONTENT_PUBLIC_BROWSER_GEOLOCATION_PROVIDER_H_
 #define CONTENT_PUBLIC_BROWSER_GEOLOCATION_PROVIDER_H_
 
 #include <memory>
 
 #include "base/callback_list.h"
 #include "content/common/content_export.h"
 
 namespace content {
+class AccessTokenStore;
 struct Geoposition;
+class LocationProvider;
 
 // This is the main API to the geolocation subsystem. The application will hold
 // a single instance of this class and can register multiple clients to be
 // notified of location changes:
 // * Callbacks are registered by AddLocationUpdateCallback() and will keep
 //   receiving updates until the returned subscription object is destructed.
 // The application must instantiate the GeolocationProvider on the UI thread and
 // must communicate with it on the same thread.
 // The underlying location arbitrator will only be enabled whilst there is at
 // least one registered observer or pending callback (and only after
 // UserDidOptIntoLocationServices). The arbitrator and the location providers it
 // uses run on a separate Geolocation thread.
 class GeolocationProvider {
  public:
+  // An embedder of Geolocation may override these class' methods to provide
+  // specific functionality.
+  class CONTENT_EXPORT Delegate {

[jam, 2016/06/28 18:08:21]

nit: I realize this is moving to device/. I would encourage you to make this to
be a separate header (i.e. geolocation_delegate.) for two reasons:
1) it can be overridden and forward declared without including the this header
2) once you move this to device/geolocation, there's no more need for an
interface/impl split of GeolocationProvider since it's out of content. so more
stuff will move to this parent class.

+   public:
+    // Returns true if the location API should use network-based location
+    // approximation in addition to the system provider, if any.
+    virtual bool UseNetworkLocationProviders();
+
+    // Creates a new AccessTokenStore for geolocation. May return nullptr.
+    // TODO(mcasas): consider changing it return type to std::unique_ptr<> to
+    // clarify ownership, https://crbug.com/623114.
+    virtual AccessTokenStore* CreateAccessTokenStore();
+
+    // Allows an embedder to return its own LocationProvider implementation.
+    // Return nullptr to use the default one for the platform to be created.
+    // Caller takes ownership of the returned LocationProvider. FYI: Used by an
+    // external project; please don't remove. Contact Viatcheslav Ostapenko at
+    // sl.ostapenko@samsung.com for more information.
+    // TODO(mcasas): return std::unique_ptr<> instead, https://crbug.com/623132.
+    virtual LocationProvider* OverrideSystemLocationProvider();
+  };
+
   CONTENT_EXPORT static GeolocationProvider* GetInstance();
 
   typedef base::Callback<void(const Geoposition&)> LocationUpdateCallback;
   typedef base::CallbackList<void(const Geoposition&)>::Subscription
       Subscription;
 
   // |enable_high_accuracy| is used as a 'hint' for the provider preferences for
   // this particular observer, however the observer could receive updates for
   // best available locations from any active provider whilst it is registered.
   virtual std::unique_ptr<Subscription> AddLocationUpdateCallback(
@@ skipping 18 matching lines @@
   // (crbug.com/125931).
   virtual void OverrideLocationForTesting(const Geoposition& position) = 0;
 
  protected:
   virtual~GeolocationProvider() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_GEOLOCATION_PROVIDER_H_