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

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 104f8c63fab5ed61390267d391cd9352ac5a4723..9b018ee5cc4c76db850fa742a1cb29384167909d 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -3211,6 +3211,15 @@ void WebContentsImpl::SetIsLoading(RenderViewHost* render_view_host,
       type, Source<NavigationController>(&controller_), det);
 }
 
+void WebContentsImpl::MoveSelectionExtent(const gfx::Point& position) {
+  RenderFrameHost* focused_frame = GetFocusedFrame();
+  if (!focused_frame)
+    return;
+
+  focused_frame->Send(new InputMsg_MoveSelectionExtent(
+      focused_frame->GetRoutingID(), position));
+}
+
 void WebContentsImpl::SelectRange(const gfx::Point& start,
                                   const gfx::Point& end) {
   RenderFrameHost* focused_frame = GetFocusedFrame();