Change media galleries to external file system type to add toURL support

chrome/browser/media_galleries/media_file_system_context.h

Index: chrome/browser/media_galleries/media_file_system_context.h
diff --git a/chrome/browser/media_galleries/media_file_system_context.h b/chrome/browser/media_galleries/media_file_system_context.h
index 0ecafd63f7d5fc4d5bfbc23d1ce0cb1949294578..a430b31bd9df9ffa4a76819569dc5cb61373ebbf 100644
--- a/chrome/browser/media_galleries/media_file_system_context.h
+++ b/chrome/browser/media_galleries/media_file_system_context.h
@@ -19,13 +19,18 @@ class MediaFileSystemContext {
  public:
   virtual ~MediaFileSystemContext() {}
 
-  // Register a new media file system for |path| and return the corresponding
-  // filesystem ID.
-  virtual std::string RegisterFileSystem(
-      const std::string& device_id, const base::FilePath& path) = 0;
-
-  // Revoke the passed |fsid|.
-  virtual void RevokeFileSystem(const std::string& fsid) = 0;
+  // Register a new media file system for |path| as |fs_name|.
+  virtual bool RegisterFileSystem(const std::string& device_id,
+                                  const std::string& fs_name,
+                                  const base::FilePath& path) = 0;
+
+  // Revoke the passed |fs_name|.
+  virtual void RevokeFileSystem(const std::string& fs_name) = 0;
+
+  // Return the mount point root for the given |fs_name|. Returns an empty path
+  // if |fs_name| is not valid.
+  virtual base::FilePath GetRegisteredPath(
+      const std::string& fs_name) const = 0;
 };
 
 #endif  // CHROME_BROWSER_MEDIA_GALLERIES_MEDIA_FILE_SYSTEM_CONTEXT_H_