Fix touch in software mirror mode when there is no internal display

ash/touch/touch_transformer_controller.cc

Index: ash/touch/touch_transformer_controller.cc
diff --git a/ash/touch/touch_transformer_controller.cc b/ash/touch/touch_transformer_controller.cc
index aa6475bb8384eb9a55d58330c256cabaf1978b9c..d88416e6feb9146f2729ed1a597df3d2ece1993c 100644
--- a/ash/touch/touch_transformer_controller.cc
+++ b/ash/touch/touch_transformer_controller.cc
@@ -204,8 +204,8 @@ void TouchTransformerController::UpdateTouchTransformer() const {
       RootWindowController::ForWindow(root)->ash_host()->UpdateDisplayID(
           display1_id, display2_id);
       DisplayInfo source_display =
-          gfx::Display::InternalDisplayId() == display1_id ?
-          display1 : display2;
+          display_controller->GetPrimaryDisplayId() == display1_id ? display1
+                                                                   : display2;

[oshima, 2015/02/27 22:13:54]

primary display can be external on the device that have internal display. I
think you need to handle both cases (use internal, or use primary when no
internal)

[pkotwicz, 2015/03/01 01:51:14]

That is true. However, in software mirror mode, if the device has an internal
display, the internal display is guaranteed to be the primary display.

The primary display is updated in DisplayController::OnDisplayRemoved()
In software mirror mode, |DisplayManager::displays_| has just one entry

[pkotwicz, 2015/03/01 03:32:50]

Even if the internal display is not the primary display in software mirror mode
and the device has an internal display, this code does the right thing.

On Ozone, the internal display is always the primary display but for very subtle
reasons. Which display is the source display / primary display depends on:
- The display IDs of both displays
- The order of |NativeDisplayDelegateDri::cached_displays_|
See
https://code.google.com/p/chromium/codesearch#chromium/src/ash/display/displa...

       // Mapping from framebuffer size to the source display's native
       // resolution.
       device_manager->UpdateTouchInfoForDisplay(