Media Galleries: Add more tests for media gallery names.

chrome/browser/media_gallery/media_file_system_registry.h

Index: chrome/browser/media_gallery/media_file_system_registry.h
===================================================================
--- chrome/browser/media_gallery/media_file_system_registry.h	(revision 173083)
+++ chrome/browser/media_gallery/media_file_system_registry.h	(working copy)
@@ -91,6 +91,11 @@
 
   std::string GetTransientIdForDeviceId(const std::string& device_id) const;
 
+  // Keys used in gallery names, which are JSON strings.
+  static const char kDeviceIdKey[];
+  static const char kGalleryIdKey[];
+  static const char kNameKey[];
+
  private:
   friend class TestMediaFileSystemContext;
   class MediaFileSystemContextImpl;