Change the meaning of SelectFileDialog.support_drive: it means Drive-aware callers.

ui/shell_dialogs/select_file_dialog.h

 // Copyright (c) 2013 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 UI_SHELL_DIALOGS_SELECT_FILE_DIALOG_H_
 #define UI_SHELL_DIALOGS_SELECT_FILE_DIALOG_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 109 matching lines @@
     std::vector<std::vector<base::FilePath::StringType> > extensions;
 
     // Overrides the system descriptions of the specified extensions. Entries
     // correspond to |extensions|; if left blank the system descriptions will
     // be used.
     std::vector<base::string16> extension_description_overrides;
 
     // Specifies whether there will be a filter added for all files (i.e. *.*).
     bool include_all_files;
 
-    // Specifies whether the caller can support files/folders that are on Drive.
+    // Specifies whether the caller can directly support file paths pointing to
+    // files/folders on Google Drive. If the flag is true, the file dialog does
+    // nothing special; just returns a Drive path. If it is false, the dialog
+    // creates a local replica of the Drive file and returns its path, so that
+    // the caller can use it without any difference than when it were local.
     bool support_drive;
   };
 
   // Selects a File.
   // Before doing anything this function checks if FileBrowsing is forbidden
   // by Policy. If so, it tries to show an InfoBar and behaves as though no File
   // was selected (the user clicked `Cancel` immediately).
   // Otherwise it will start displaying the dialog box. This will also
   // block the calling window until the dialog box is complete. The listener
   // associated with this object will be notified when the selection is
@@ skipping 69 matching lines @@
   virtual bool HasMultipleFileTypeChoicesImpl() = 0;
 
   scoped_ptr<SelectFilePolicy> select_file_policy_;
 
   DISALLOW_COPY_AND_ASSIGN(SelectFileDialog);
 };
 
 }  // namespace ui
 
 #endif  // UI_SHELL_DIALOGS_SELECT_FILE_DIALOG_H_