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

ui/gfx/render_text_mac.mm

Index: ui/gfx/render_text_mac.mm
diff --git a/ui/gfx/render_text_mac.mm b/ui/gfx/render_text_mac.mm
index e380333c8c88f471ac158b6c5f30bfc043d3d371..14852046df0173e44f81c6fa335dc78a0a9adec2 100644
--- a/ui/gfx/render_text_mac.mm
+++ b/ui/gfx/render_text_mac.mm
@@ -448,4 +448,17 @@
   runs_valid_ = false;
 }
 
+bool RenderTextMac::GetDecoratedTextForRange(
+    const Range& range,
+    DecoratedText* decorated_text) const {
+  // TODO(karandeepb): This is not invoked on any codepath currently. Style the
+  // returned text if need be.
+  if (obscured())
+    return false;
+
+  decorated_text->attributes.clear();
+  decorated_text->text = GetTextFromRange(range);
+  return true;
+}
+
 }  // namespace gfx