Introduce user customization of external HighDPI mode for 4K monitor.

ash/display/display_info.h

Index: ash/display/display_info.h
diff --git a/ash/display/display_info.h b/ash/display/display_info.h
index a8bca41e4d7bf7371034a1183728d51378016572..627e8695dfaf2b03fdfbfbe355a6732c5f98c5ea 100644
--- a/ash/display/display_info.h
+++ b/ash/display/display_info.h
@@ -24,10 +24,18 @@ struct ASH_EXPORT DisplayMode {
               bool interlaced,
               bool native);
 
+  // Returns the size in DIP which isvisible to the user.
+  gfx::Size GetSizeInDIP() const;
+
+  bool operator==(const DisplayMode& other) const;

[oshima, 2014/07/31 02:16:52]

can you add comment that this is necessary for stl compatibility ? (style guide
still recommends not to use operator overloading in general)

[Jun Mukai, 2014/07/31 04:57:52]

This was added for options handler (check if an option is 'selected' or not).  I
missed the style guide. Renamed to a normal method.

[oshima, 2014/07/31 18:52:37]

I'm personally fine with this as you used this in std::find(. I'll leave this to
 you.

+
   gfx::Size size;      // Physical pixel size of the display.
   float refresh_rate;  // Refresh rate of the display, in Hz.
   bool interlaced;     // True if mode is interlaced.
   bool native;         // True if mode is native mode of the display.
+  float ui_scale;      // The UI scale factor of the mode.
+                       // TODO(mukai|oshima): merge to device_scale_factor.

[oshima, 2014/07/31 02:16:52]

should we?

[Jun Mukai, 2014/07/31 04:57:52]

removed because you're suspicious.

+  float device_scale_factor;  // The device scale factor of the mode.
 };
 
 // DisplayInfo contains metadata for each display. This is used to