Re-implement overscan & Implement Display Rotation

ash/test/ash_test_base.cc

Index: ash/test/ash_test_base.cc
diff --git a/ash/test/ash_test_base.cc b/ash/test/ash_test_base.cc
index a1cf63740a66ce77cc3e83cc8d226bcaedf8f8f4..5c3e7e52eb37b7136fa75443385e28533c0bf8ba 100644
--- a/ash/test/ash_test_base.cc
+++ b/ash/test/ash_test_base.cc
@@ -107,12 +107,16 @@ void AshTestBase::SetUp() {
   message_center::MessageCenter::Initialize();
 #endif
   ash::Shell::CreateInstance(test_shell_delegate_);
+  Shell* shell = Shell::GetInstance();
+  test::DisplayManagerTestApi(shell->display_manager()).
+      DisableChangeDisplayUponHostResize();
+
   Shell::GetPrimaryRootWindow()->Show();
   Shell::GetPrimaryRootWindow()->ShowRootWindow();
   // Move the mouse cursor to far away so that native events doesn't
   // interfere test expectations.
   Shell::GetPrimaryRootWindow()->MoveCursorTo(gfx::Point(-1000, -1000));
-  Shell::GetInstance()->cursor_manager()->EnableMouseEvents();
+  shell->cursor_manager()->EnableMouseEvents();
 
 #if defined(OS_WIN)
   if (base::win::GetVersion() >= base::win::VERSION_WIN8) {