Add the partial screen magnifier to Chrome OS.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index feb1c994d07c08c9b62da53c5c8372bd88aa6a41..f7aa1730ebb33855a9333954976e048f9f72717c 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -21,6 +21,7 @@
 #include "ash/focus_cycler.h"
 #include "ash/high_contrast/high_contrast_controller.h"
 #include "ash/magnifier/magnification_controller.h"
+#include "ash/magnifier/partial_magnification_controller.h"
 #include "ash/root_window_controller.h"
 #include "ash/screen_ash.h"
 #include "ash/shell_delegate.h"
@@ -263,6 +264,7 @@ Shell::~Shell() {
   // Alphabetical.
   drag_drop_controller_.reset();
   magnification_controller_.reset();
+  partial_magnification_controller_.reset();
   power_button_controller_.reset();
   session_state_controller_.reset();
   resize_shadow_controller_.reset();
@@ -462,7 +464,10 @@ void Shell::Init() {
   AddEnvEventFilter(window_modality_controller_.get());
 
   magnification_controller_.reset(
-      internal::MagnificationController::CreateInstance());
+      MagnificationController::CreateInstance());
+
+  partial_magnification_controller_.reset(
+      new PartialMagnificationController());
 
   high_contrast_controller_.reset(new HighContrastController);
   video_detector_.reset(new VideoDetector);