Implement Desktop Media Picker (Mac version) for Desktop Capture API

chrome/browser/media/desktop_media_picker_model.h

Index: chrome/browser/media/desktop_media_picker_model.h
diff --git a/chrome/browser/media/desktop_media_picker_model.h b/chrome/browser/media/desktop_media_picker_model.h
index 7773c3d9476b8aa8f6e687760ca9722c019f5c52..c7d0e5626445850af40a24e0ef2c1ec99e49c1d9 100644
--- a/chrome/browser/media/desktop_media_picker_model.h
+++ b/chrome/browser/media/desktop_media_picker_model.h
@@ -71,11 +71,15 @@ class DesktopMediaPickerModel {
   // enumerated. After the initial enumeration the model will be refreshed based
   // on the update period, and notifications generated only for changes in the
   // model.
-  void StartUpdating(Observer* observer);
+  virtual void StartUpdating(Observer* observer);
 
   int source_count() const { return sources_.size(); }
   const Source& source(int index) const { return sources_.at(index); }
 
+ protected:
+  // Current list of sources.
+  std::vector<Source> sources_;
+
  private:
   class Worker;
   friend class Worker;
@@ -124,9 +128,6 @@ class DesktopMediaPickerModel {
   // after the model is destroyed.
   scoped_ptr<Worker> worker_;
 
-  // Current list of sources.
-  std::vector<Source> sources_;
-
   base::WeakPtrFactory<DesktopMediaPickerModel> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopMediaPickerModel);