Fix font sizes being incorrect when using --force-device-scale-factor.

ui/display/win/screen_win.h

Index: ui/display/win/screen_win.h
diff --git a/ui/display/win/screen_win.h b/ui/display/win/screen_win.h
index 94379e055f3245938004c1689456f803f0aad7c9..5b6682152963a9098879c41dcec97824ba71b2a3 100644
--- a/ui/display/win/screen_win.h
+++ b/ui/display/win/screen_win.h
@@ -102,6 +102,13 @@ class DISPLAY_EXPORT ScreenWin : public Screen {
   // Returns |hwnd|'s scale factor.
   static float GetScaleFactorForHWND(HWND hwnd);
 
+  // Returns the system's global scale factor. In most cases you should prefer

[robliao, 2017/02/15 18:43:16]

Possible rephrasing. What do you think?

Returns the system's global scale factor ignoring --force-device-scale-factor.
Only call this if you are working with Windows metrics global to the display.
Otherwise you should call GetScaleFactorForHWND() to handle per-monitor scale
factors.

[Bret, 2017/02/15 20:43:16]

Yeah yours is clearer. I edited it slightly.

+  // GetScaleFactorForHWND (so as to be per-monitor aware) but occasionally
+  // we need this value specifically, usually when working with a value from
+  // SystemParametersInfo. Also ignores --force-device-scale-factor since that
+  // interferes with working directly from the system.
+  static float GetSystemScaleFactor();
+
   // Returns the HWND associated with the NativeView.
   virtual HWND GetHWNDFromNativeView(gfx::NativeView window) const;