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

content/browser/android/content_view_core_impl.h

Index: content/browser/android/content_view_core_impl.h
diff --git a/content/browser/android/content_view_core_impl.h b/content/browser/android/content_view_core_impl.h
index cfa424bce77f6997b69c8ac3531f9452098e242c..571e8dc7c8edc7ac5ef715c7189006bd67bb24c8 100644
--- a/content/browser/android/content_view_core_impl.h
+++ b/content/browser/android/content_view_core_impl.h
@@ -274,6 +274,8 @@ class ContentViewCoreImpl : public ContentViewCore,
   void AttachLayer(scoped_refptr<cc::Layer> layer);
   void RemoveLayer(scoped_refptr<cc::Layer> layer);
 
+  void MoveSelectionExtent(const gfx::PointF& position);
+
   void SelectBetweenCoordinates(const gfx::PointF& start,
                                 const gfx::PointF& end);