Simplify Android geolocation permission checks

chrome/browser/geolocation/geolocation_permission_context_android.h

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Copyright 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 CHROME_BROWSER_GEOLOCATION_GEOLOCATION_PERMISSION_CONTEXT_ANDROID_H_
 #define CHROME_BROWSER_GEOLOCATION_GEOLOCATION_PERMISSION_CONTEXT_ANDROID_H_
 
+// The flow for geolocation permissions on Android needs to take into account
+// the global geolocation settings so it differs from the desktop one. It
+// works as follows.
+// GeolocationPermissionContextAndroid::DecidePermission intercepts the flow in
+// the UI thread, and posts a task to the blocking pool to CheckSystemLocation.
+// CheckSystemLocation will in fact check several possible settings
+//     - The global system geolocation setting
+//     - The Google location settings on pre KK devices
+//     - An old internal Chrome setting on pre-JB MR1 devices
+// With all that information it will decide if system location is enabled.
+// If enabled, it proceeds with the per site flow via
+// GeolocationPermissionContext (which will check per site permissions, create
+// infobars, etc.).
+//
+// Otherwise the permission is already decided.
+
+// There is a bit of thread jumping since some of the permissions (like the
+// per site settings) are queried on the UI thread while the system level
+// permissions are considered I/O and thus checked in the blocking thread pool.
+
 #include "chrome/browser/content_settings/permission_request_id.h"
 #include "chrome/browser/geolocation/geolocation_permission_context.h"
 #include "url/gurl.h"
 
 namespace content {
 class WebContents;
 }
 
 class GoogleLocationSettingsHelper;
 
-// Android-specific geolocation permission flow, taking into account the
-// Google Location Settings, if available.
+
 class GeolocationPermissionContextAndroid
     : public GeolocationPermissionContext {
  public:
   explicit GeolocationPermissionContextAndroid(Profile* profile);
 
  private:
   struct PermissionRequestInfo {
     PermissionRequestInfo();
 
     PermissionRequestID id;
     GURL requesting_frame;
     bool user_gesture;
     GURL embedder;
   };
 
   friend class GeolocationPermissionContext;
 
   virtual ~GeolocationPermissionContextAndroid();
 
   // GeolocationPermissionContext implementation:
   virtual void DecidePermission(content::WebContents* web_contents,
                                 const PermissionRequestID& id,
                                 const GURL& requesting_frame,
                                 bool user_gesture,
                                 const GURL& embedder,
-                                const std::string& accept_button_label,
                                 base::Callback<void(bool)> callback) OVERRIDE;
 
-  virtual void PermissionDecided(const PermissionRequestID& id,
-                                 const GURL& requesting_frame,
-                                 const GURL& embedder,
-                                 base::Callback<void(bool)> callback,
-                                 bool allowed) OVERRIDE;
-
   void ProceedDecidePermission(content::WebContents* web_contents,
                                const PermissionRequestInfo& info,
-                               const std::string& accept_button_label,
                                base::Callback<void(bool)> callback);
 
   scoped_ptr<GoogleLocationSettingsHelper> google_location_settings_helper_;
 
  private:
-  void CheckMasterLocation(content::WebContents* web_contents,
+  void CheckSystemLocation(content::WebContents* web_contents,
                            const PermissionRequestInfo& info,
                            base::Callback<void(bool)> callback);
 
   DISALLOW_COPY_AND_ASSIGN(GeolocationPermissionContextAndroid);
 };
 
 #endif  // CHROME_BROWSER_GEOLOCATION_GEOLOCATION_PERMISSION_CONTEXT_ANDROID_H_