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

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 2b8bcf0f6e9019f91f36b77e5f9a36f3ce3f46a3..86d9a3a75d3761d04d8383417b912e998e2fddbb 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -824,6 +824,7 @@ bool RenderFrameImpl::OnMessageReceived(const IPC::Message& msg) {
     IPC_MESSAGE_HANDLER(InputMsg_SelectAll, OnSelectAll)
     IPC_MESSAGE_HANDLER(InputMsg_SelectRange, OnSelectRange)
     IPC_MESSAGE_HANDLER(InputMsg_Unselect, OnUnselect)
+    IPC_MESSAGE_HANDLER(InputMsg_MoveSelectionExtent, OnMoveSelectionExtent)
     IPC_MESSAGE_HANDLER(InputMsg_Replace, OnReplace)
     IPC_MESSAGE_HANDLER(InputMsg_ReplaceMisspelling, OnReplaceMisspelling)
     IPC_MESSAGE_HANDLER(InputMsg_ExtendSelectionAndDelete,
@@ -1224,6 +1225,15 @@ void RenderFrameImpl::OnUnselect() {
   frame_->executeCommand(WebString::fromUTF8("Unselect"), GetFocusedElement());
 }
 
+void RenderFrameImpl::OnMoveSelectionExtent(const gfx::Point& point) {
+  // This IPC is dispatched by RenderWidgetHost, so use its routing id.
+  Send(new ViewHostMsg_MoveSelectionExtent_ACK(
+      GetRenderWidget()->routing_id()));
+
+  base::AutoReset<bool> handling_select_range(&handling_select_range_, true);
+  frame_->moveSelectionExtent(point);
+}
+
 void RenderFrameImpl::OnReplace(const base::string16& text) {
   if (!frame_->hasSelection())
     frame_->selectWordAroundCaret();