Add ScreenWin::GetSystemMetricsForHwnd

ui/display/win/screen_win.cc

Index: ui/display/win/screen_win.cc
diff --git a/ui/display/win/screen_win.cc b/ui/display/win/screen_win.cc
index b518fd4d3daa4c91ee1ef2e113574069869a7832..47911905022d894583cb42b2088a8d7375f6fe18 100644
--- a/ui/display/win/screen_win.cc
+++ b/ui/display/win/screen_win.cc
@@ -295,6 +295,22 @@ gfx::Size ScreenWin::DIPToScreenSize(HWND hwnd, const gfx::Size& dip_size) {
   return ScaleToCeiledSize(dip_size, scale_factor);
 }
 
+// static
+int ScreenWin::GetSystemMetricsForHwnd(HWND hwnd, int metric) {
+  // GetSystemMetrics returns screen values based off of the primary monitor's
+  // DPI. This will further scale based off of the DPI for |hwnd|.
+  if (!g_screen_win_instance)

[oshima, 2016/06/30 19:06:12]

is this for unit test case?

[robliao, 2016/06/30 19:20:24]

Yup. This is for the unit tests.

+    return ::GetSystemMetrics(metric);
+
+  Display primary_display(g_screen_win_instance->GetPrimaryDisplay());
+  int system_metrics_result = g_screen_win_instance->GetSystemMetrics(metric);
+
+  float scale_factor = hwnd
+      ? GetScaleFactorForHWND(hwnd) / primary_display.device_scale_factor()

[oshima, 2016/06/30 19:06:12]

calling this "scale factor" is confusing. Can you call it like
the "scale_to_primary_metrics" or something like that?

[robliao, 2016/06/30 19:20:24]

I went with metrics_relative_scale_factor. How's that?

+      : 1.0f;
+  return static_cast<int>(std::round(system_metrics_result * scale_factor));
+}
+
 HWND ScreenWin::GetHWNDFromNativeView(gfx::NativeView window) const {
   NOTREACHED();
   return nullptr;
@@ -419,6 +435,10 @@ HWND ScreenWin::GetRootWindow(HWND hwnd) const {
   return ::GetAncestor(hwnd, GA_ROOT);
 }
 
+int ScreenWin::GetSystemMetrics(int metric) const {
+  return ::GetSystemMetrics(metric);
+}
+
 void ScreenWin::OnWndProc(HWND hwnd,
                           UINT message,
                           WPARAM wparam,