fix build with enable_web_intents=0 on chromeos

chrome/browser/chromeos/extensions/file_browser_private_api.h

Index: chrome/browser/chromeos/extensions/file_browser_private_api.h
diff --git a/chrome/browser/chromeos/extensions/file_browser_private_api.h b/chrome/browser/chromeos/extensions/file_browser_private_api.h
index eeb05003e07c76f45e3aa4bd80a4e1b1e5e3a69a..62f1ec9c36b80d9a612877683111433e96712288 100644
--- a/chrome/browser/chromeos/extensions/file_browser_private_api.h
+++ b/chrome/browser/chromeos/extensions/file_browser_private_api.h
@@ -198,10 +198,12 @@ class GetFileTasksFileBrowserFunction : public AsyncExtensionFunction {
                          ListValue* result_list,
                          bool* default_already_set);
 
+#if defined(ENABLE_WEB_INTENTS)
   // Find the list of Web Intent tasks that can be used with the given file
   // types, appending them to the |result_list|.
   bool FindWebIntentTasks(const std::vector<FilePath>& file_paths,
                           ListValue* result_list);
+#endif
 
   // Find the list of app file handlers that can be used with the given file
   // types, appending them to the |result_list|.