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

content/browser/renderer_host/input/input_router_impl.h

Index: content/browser/renderer_host/input/input_router_impl.h
diff --git a/content/browser/renderer_host/input/input_router_impl.h b/content/browser/renderer_host/input/input_router_impl.h
index 0f7b023bfd6fe3e7233a5bd23e43d3d33acf0cee..a025f11288e3c8de32cdd718040f60eb7fa5552b 100644
--- a/content/browser/renderer_host/input/input_router_impl.h
+++ b/content/browser/renderer_host/input/input_router_impl.h
@@ -99,6 +99,7 @@ private:
 
   bool SendMoveCaret(scoped_ptr<IPC::Message> message);
   bool SendSelectRange(scoped_ptr<IPC::Message> message);
+  bool SendMoveSelectionExtent(scoped_ptr<IPC::Message> message);
   bool Send(IPC::Message* message);
 
   // Filters and forwards |input_event| to the appropriate handler.
@@ -152,6 +153,7 @@ private:
   void OnDidOverscroll(const DidOverscrollParams& params);
   void OnMsgMoveCaretAck();
   void OnSelectRangeAck();
+  void OnMoveSelectionExtentAck();
   void OnHasTouchEventHandlers(bool has_handlers);
   void OnSetTouchAction(TouchAction touch_action);
 
@@ -221,6 +223,14 @@ private:
   // (Similar to |next_mouse_move_|.) The next SelectRange to send, if any.
   scoped_ptr<IPC::Message> next_selection_range_;
 
+  // (Similar to |mouse_move_pending_|.) True while waiting for
+  // MoveSelectionExtent_ACK.
+  bool move_selection_extent_pending_;
+
+  // (Similar to |next_mouse_move_|.) The next MoveSelectionExtent to send, if
+  // any.
+  scoped_ptr<IPC::Message> next_selection_extent_move_;
+
   // (Similar to |mouse_move_pending_|.) True while waiting for MoveCaret_ACK.
   bool move_caret_pending_;