Standardize IME callbacks for off-screen rendering (issue #1675)

tests/cefclient/browser/browser_window_osr_gtk.h

@@ -76,6 +76,10 @@ class BrowserWindowOsrGtk : public BrowserWindow,
                      int x, int y) OVERRIDE;
   void UpdateDragCursor(CefRefPtr<CefBrowser> browser,
                         CefRenderHandler::DragOperation operation) OVERRIDE;
+  void OnImeCompositionRangeChanged(
+      CefRefPtr<CefBrowser> browser,
+      const CefRange& selection_range,
+      const CefRenderHandler::RectList& character_bounds) OVERRIDE;
 
  private:
   // Create the GTK GlArea.