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..c0aa7071a3c32a5751642063fcf476cf4070afea 100644
--- a/content/renderer/render_frame_impl.h
+++ b/content/renderer/render_frame_impl.h
@@ -524,8 +524,9 @@ class CONTENT_EXPORT RenderFrameImpl
   void OnPasteAndMatchStyle();
   void OnDelete();
   void OnSelectAll();
-  void OnSelectRange(const gfx::Point& start, const gfx::Point& end);
+  void OnSelectRange(const gfx::Point& base, const gfx::Point& extent);
   void OnUnselect();
+  void OnMoveRangeSelectionExtent(const gfx::Point& point);
   void OnReplace(const base::string16& text);
   void OnReplaceMisspelling(const base::string16& text);
   void OnCSSInsertRequest(const std::string& css);