Update touch selection to only modify one selection point at a time.

content/renderer/render_frame_impl.h

Index: content/renderer/render_frame_impl.h
diff --git a/content/renderer/render_frame_impl.h b/content/renderer/render_frame_impl.h
index 2eeb0aa72bb1ffdff98ba17e24b1a86a4efd051b..c51555106b05d74bff8ec8263c2ae72dc203f5ca 100644
--- a/content/renderer/render_frame_impl.h
+++ b/content/renderer/render_frame_impl.h
@@ -526,6 +526,7 @@ class CONTENT_EXPORT RenderFrameImpl
   void OnSelectAll();
   void OnSelectRange(const gfx::Point& start, const gfx::Point& end);
   void OnUnselect();
+  void OnMoveSelectionExtent(const gfx::Point& point);
   void OnReplace(const base::string16& text);
   void OnReplaceMisspelling(const base::string16& text);
   void OnCSSInsertRequest(const std::string& css);