Stubs for triggering the LSD in Clank

chrome/browser/android/location_settings.h

 // Copyright 2015 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_ANDROID_LOCATION_SETTINGS_H_
 #define CHROME_BROWSER_ANDROID_LOCATION_SETTINGS_H_
 
+#include "base/callback.h"
 #include "base/macros.h"
 
 namespace content {
 class WebContents;
 }
 
 // This class determines whether Chrome can access the device's location,
 // i.e. whether location is enabled system-wide on the device.
 class LocationSettings {
  public:
   virtual ~LocationSettings() {}
 
   // Returns true if:
   //  - Location is enabled system-wide (in Android settings)
   //  - The necessary location permission are granted to Chrome, or if Chrome
   //    still has the ability to request the permissions to be granted.
   virtual bool CanSitesRequestLocationPermission(
       content::WebContents* web_contents) = 0;
+
+  // Returns true iff a prompt can be triggered to ask the user to turn on the
+  // system location setting on their device.
+  // In particular, returns false if the system location setting is already
+  // enabled or if some of the features required to trigger a system location
+  // setting prompt are not available.
+  virtual bool CanPromptToEnableSystemLocationSetting() = 0;
+
+  // An enum to describe the context in which a system location setting prompt
+  // is triggered to allow the prompt UI to be customized to the given context.
+  //
+  // Keep in sync with the LocationSettingsDialogContext IntDef in

[Ted C, 2017/03/02 00:21:56]

We have a system to generate java int constants based on a C++ enum.

If you look for GENERATED_JAVA_ENUM_PACKAGE, you'll see other examples.

The problem is there are no C++ class in components/location/android, but I
think we should consider them here as the layering is very weird.

If that is infeasible right now, please add a TODO and address it after branch.

[qfiard, 2017/03/02 13:28:13]

Done, nice!

+  // //components/location/android/java/src/org/chromium/components/location/LocationUtils.java
+  enum LocationSettingsDialogContext {
+    // Default context.
+    DEFAULT = 1,
+    // Prompt triggered in the context of a search.
+    SEARCH = 2,
+  };
+
+  // An enum to describe the outcome of a location setting prompt triggered by
+  // PromptToEnableSystemLocationSetting().
+  //
+  // Keep in sync with the LocationSettingsDialogOutcome IntDef in
+  // //components/location/android/java/src/org/chromium/components/location/LocationUtils.java
+  enum LocationSettingsDialogOutcome {
+    // The user accepted the prompt and the system location setting has been
+    // flipped to granted.
+    GRANTED = 1,
+
+    // The user rejected the prompt and the system location setting has not been
+    // flipped.
+    DENIED = 2,
+
+    // The prompt could not be triggered.
+    // When CanPromptToEnableSystemLocationSetting() returns true, this should
+    // only happen in exceptional circonstances, e.g.
+    // - In the case of a race condition where the system location setting is
+    // flipped elsewhere before the prompt could be triggered;
+    // - In the case where some of the features required to trigger a system
+    // location setting prompt became unavailable or unresponsive after the
+    // response from CanPromptToEnableSystemLocationSetting() was received.
+    NO_PROMPT = 3,
+  };
+
+  typedef base::OnceCallback<void(LocationSettingsDialogOutcome)>
+      LocationSettingsDialogOutcomeCallback;
+
+  // Triggers a prompt to ask the user to turn on the system location setting on
+  // their device.
+  // The prompt will be triggered in the activity of the web contents.
+  virtual void PromptToEnableSystemLocationSetting(

[Ted C, 2017/03/02 00:21:56]

I would add comments about the lifetime of this.  This could potentially trigger
a new Android widget whose lifecycle is outside of our control.  If the owner of
the callback has any chance of being destroyed during this process, they should
be careful to use the proper weak ptr semantics to avoid crashing here.

[qfiard, 2017/03/02 13:28:13]

Done.

+      const LocationSettingsDialogContext prompt_context,
+      content::WebContents* web_contents,
+      LocationSettingsDialogOutcomeCallback callback) = 0;
 };
 
 #endif  // CHROME_BROWSER_ANDROID_LOCATION_SETTINGS_H_