Disable touch calibration on external touchscreen.

ash/display/display_manager.cc

Index: ash/display/display_manager.cc
diff --git a/ash/display/display_manager.cc b/ash/display/display_manager.cc
index 1522564706f59b8c9ad84077ef1406f4676b022d..04836e2463432765d3bf14c8fde3586a8fe93e26 100644
--- a/ash/display/display_manager.cc
+++ b/ash/display/display_manager.cc
@@ -334,9 +334,11 @@ RootWindow* DisplayManager::CreateRootWindowForDisplay(
     const gfx::Display& display) {
   static int root_window_count = 0;
 
-  RootWindow::CreateParams params(display.bounds_in_pixel());
+  RootWindow::CreateParams params(display.bounds_in_pixel(),
+                                  IsInternalDisplayId(display.id()));
   params.host = Shell::GetInstance()->root_window_host_factory()->
-      CreateRootWindowHost(display.bounds_in_pixel());
+      CreateRootWindowHost(display.bounds_in_pixel(),
+                           IsInternalDisplayId(display.id()));
   aura::RootWindow* root_window = new aura::RootWindow(params);
   root_window->SetName(StringPrintf("RootWindow-%d", root_window_count++));