Use WS_POPUP for ash_unittests

ui/aura/root_window_host_win.cc

Index: ui/aura/root_window_host_win.cc
diff --git a/ui/aura/root_window_host_win.cc b/ui/aura/root_window_host_win.cc
index 1109b72e103340b6d681eb59931cc9f5e0e027cc..e8d50f95cdb5910bc6d92e90b07832a4a95bb53a 100644
--- a/ui/aura/root_window_host_win.cc
+++ b/ui/aura/root_window_host_win.cc
@@ -14,11 +14,18 @@
 #include "ui/base/cursor/cursor_loader_win.h"
 #include "ui/base/events/event.h"
 #include "ui/base/view_prop.h"
+#include "ui/gfx/display.h"
+#include "ui/gfx/screen.h"
 
 using std::max;
 using std::min;
 
 namespace aura {
+namespace {
+
+bool use_popup_as_root_window_for_test = false;
+
+}  // namespace
 
 // static
 RootWindowHost* RootWindowHost::Create(const gfx::Rect& bounds) {
@@ -37,6 +44,8 @@ RootWindowHostWin::RootWindowHostWin(const gfx::Rect& bounds)
       has_capture_(false),
       saved_window_style_(0),
       saved_window_ex_style_(0) {
+  if (use_popup_as_root_window_for_test)
+    set_window_style(WS_POPUP);
   Init(NULL, bounds);
   SetWindowText(hwnd(), L"aura::RootWindow!");
 }
@@ -121,11 +130,19 @@ void RootWindowHostWin::SetBounds(const gfx::Rect& bounds) {
   SetWindowPos(
       hwnd(),
       NULL,
-      0,
-      0,
+      window_rect.left,
+      window_rect.top,
       window_rect.right - window_rect.left,
       window_rect.bottom - window_rect.top,
       SWP_NOMOVE | SWP_NOOWNERZORDER | SWP_NOREDRAW | SWP_NOREPOSITION);
+
+  // Explicity call OnHostResized when the scale has changed because
+  // the window size may not have changed.
+  float current_scale = delegate_->GetDeviceScaleFactor();
+  float new_scale = gfx::Screen::GetScreenFor(delegate_->AsRootWindow())->
+      GetDisplayNearestWindow(delegate_->AsRootWindow()).device_scale_factor();
+  if (current_scale != new_scale)
+    delegate_->OnHostResized(bounds.size());
 }
 
 gfx::Point RootWindowHostWin::GetLocationOnNativeScreen() const {
@@ -281,4 +298,13 @@ void RootWindowHostWin::OnSize(UINT param, const CSize& size) {
     delegate_->OnHostResized(gfx::Size(size.cx, size.cy));
 }
 
+namespace test {
+
+// static
+void SetUsePopupAsRootWindowForTest(bool use) {
+  use_popup_as_root_window_for_test = use;
+}
+
+}  // namespace test
+
 }  // namespace aura