hi-dpi: convert _NET_WORKAREA from pixels.

ui/views/widget/desktop_aura/desktop_screen_x11.cc

Index: ui/views/widget/desktop_aura/desktop_screen_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_screen_x11.cc b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
index ed8a0f4844cd7f002c6d1c492eff05575ebedf81..1f6716890fa41535826e1b86f20aa3fab517059b 100644
--- a/ui/views/widget/desktop_aura/desktop_screen_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
@@ -20,6 +20,8 @@
 #include "ui/display/util/x11/edid_parser_x11.h"
 #include "ui/events/platform/platform_event_source.h"
 #include "ui/gfx/display.h"
+#include "ui/gfx/geometry/point_conversions.h"
+#include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/screen.h"
 #include "ui/gfx/x/x11_types.h"
@@ -315,9 +317,15 @@ std::vector<gfx::Display> DesktopScreenX11::BuildDisplaysFromXRandRInfo() {
       }
 
       if (has_work_area) {
-        gfx::Rect intersection = crtc_bounds;
-        intersection.Intersect(work_area);
-        display.set_work_area(intersection);
+        gfx::Rect intersection_in_pixels = crtc_bounds;

[sadrul, 2015/03/28 22:26:02]

Our gfx::Display API is ... confusing. Mind leaving a comment here that
SetScaleAndBounds() above would convert from pixel to DIP, but set_work_area
doesn't, and so we need to explicitly do this conversion here?

[stapelberg, 2015/03/29 14:37:19]

Done.

+        intersection_in_pixels.Intersect(work_area);
+        display.set_work_area(gfx::Rect(
+            gfx::ToFlooredPoint(
+                gfx::ScalePoint(intersection_in_pixels.origin(),
+                                1.0f / display.device_scale_factor())),
+            gfx::ToFlooredSize(
+                gfx::ScaleSize(intersection_in_pixels.size(),
+                               1.0f / display.device_scale_factor()))));
       }
 
       switch (crtc->rotation) {