Enable display rotation, magnifier in unified desktop mode

ash/display/display_controller.cc

Index: ash/display/display_controller.cc
diff --git a/ash/display/display_controller.cc b/ash/display/display_controller.cc
index 4044fe76464973527bd587b74faa68f5f90330be..898268471bc987217358f88454c0da61bb4f246d 100644
--- a/ash/display/display_controller.cc
+++ b/ash/display/display_controller.cc
@@ -17,6 +17,8 @@
 #include "ash/host/ash_window_tree_host.h"
 #include "ash/host/ash_window_tree_host_init_params.h"
 #include "ash/host/root_window_transformer.h"
+#include "ash/magnifier/magnification_controller.h"
+#include "ash/magnifier/partial_magnification_controller.h"
 #include "ash/root_window_controller.h"
 #include "ash/root_window_settings.h"
 #include "ash/screen_util.h"
@@ -367,7 +369,7 @@ aura::Window* DisplayController::GetRootWindowForDisplayId(int64 id) {
 
 AshWindowTreeHost* DisplayController::GetAshWindowTreeHostForDisplayId(
     int64 id) {
-  CHECK_EQ(1u, window_tree_hosts_.count(id));
+  CHECK_EQ(1u, window_tree_hosts_.count(id)) << "id = " << id;
   return window_tree_hosts_[id];
 }
 
@@ -640,6 +642,14 @@ void DisplayController::OnDisplayAdded(const gfx::Display& display) {
         AddWindowTreeHostForDisplay(display, AshWindowTreeHostInitParams());
     RootWindowController::CreateForSecondaryDisplay(ash_host);
 
+    // Magnifier controllers keep pointers to the current root window.
+    // Update them here to avoid accessing them later.
+    Shell::GetInstance()->magnification_controller()->SwitchTargetRootWindow(
+        ash_host->AsWindowTreeHost()->window(), false);
+    Shell::GetInstance()
+        ->partial_magnification_controller()
+        ->SwitchTargetRootWindow(ash_host->AsWindowTreeHost()->window());
+
     if (primary_tree_host_for_replace_) {
       AshWindowTreeHost* to_delete = primary_tree_host_for_replace_;
       primary_tree_host_for_replace_ = nullptr;