[Mac] Implement the system dictionary popup by implementing NSTextInput methods.

content/browser/renderer_host/render_view_host.h

Index: content/browser/renderer_host/render_view_host.h
diff --git a/content/browser/renderer_host/render_view_host.h b/content/browser/renderer_host/render_view_host.h
index cc3bfacac8fe5aa5a76f6fe00120b2b552e97818..2a8a3d5fe92549732a8c46502a368ecf9aecb5fe 100644
--- a/content/browser/renderer_host/render_view_host.h
+++ b/content/browser/renderer_host/render_view_host.h
@@ -593,7 +593,7 @@ class RenderViewHost : public RenderWidgetHost {
                                          const std::string& target);
   void OnMsgSetTooltipText(const std::wstring& tooltip_text,
                            WebKit::WebTextDirection text_direction_hint);
-  void OnMsgSelectionChanged(const std::string& text);
+  void OnMsgSelectionChanged(const std::string& text, int start, int end);
   void OnMsgPasteFromSelectionClipboard();
   void OnMsgRunJavaScriptMessage(const std::wstring& message,
                                  const std::wstring& default_prompt,