MacViews: Implement Force Touch/Mac dictionary lookup for Textfields.

ui/gfx/render_text_mac.h

Index: ui/gfx/render_text_mac.h
diff --git a/ui/gfx/render_text_mac.h b/ui/gfx/render_text_mac.h
index 7c1d67e9314adb3941cb2c0177faccf4c10b4f88..8ee4f970e2643a4d59369b747906bddceaa8a341 100644
--- a/ui/gfx/render_text_mac.h
+++ b/ui/gfx/render_text_mac.h
@@ -109,6 +109,10 @@ class GFX_EXPORT RenderTextMac : public RenderText {
   // Clears cached style. Doesn't update display text (e.g. eliding).
   void InvalidateStyle();
 
+  // RenderText:
+  bool GetStyledStringForRange(const Range& range,
+                               NativeStyledString str) const override;
+
   // The Core Text line of text. Created by |EnsureLayout()|.
   base::ScopedCFTypeRef<CTLineRef> line_;