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

ui/shell_dialogs/select_file_dialog.h

Index: ui/shell_dialogs/select_file_dialog.h
diff --git a/ui/shell_dialogs/select_file_dialog.h b/ui/shell_dialogs/select_file_dialog.h
index 3bd3c8e11b4d4c33c79f52fc3c38c6ef6cd60630..c5fc26d0ce6658e99b5a22cd296eaa2f1cfe9845 100644
--- a/ui/shell_dialogs/select_file_dialog.h
+++ b/ui/shell_dialogs/select_file_dialog.h
@@ -127,7 +127,11 @@ class SHELL_DIALOGS_EXPORT SelectFileDialog
     // 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;
   };