Add OnDisplayMetricsChanged in DisplayObserver.

ui/gfx/display_observer.h

Index: ui/gfx/display_observer.h
diff --git a/ui/gfx/display_observer.h b/ui/gfx/display_observer.h
index ca97247f9ede0a165208aa69810b65f1870c710d..92b08d5328d581720b684f381616cc19edb38605 100644
--- a/ui/gfx/display_observer.h
+++ b/ui/gfx/display_observer.h
@@ -5,6 +5,8 @@
 #ifndef UI_GFX_DISPLAY_OBSERVER_H_
 #define UI_GFX_DISPLAY_OBSERVER_H_
 
+#include <stdint.h>
+
 #include "ui/gfx/gfx_export.h"
 
 namespace gfx {
@@ -15,8 +17,14 @@ class Display;
 // |DisplaySettingsProvier|. crbug.com/122863.
 class GFX_EXPORT DisplayObserver {
  public:
-  // Called when the |display|'s bound has changed.
-  virtual void OnDisplayBoundsChanged(const Display& display) = 0;
+  enum DisplayMetric {
+    DISPLAY_METRICS_NONE = 0,
+    DISPLAY_METRICS_BOUNDS = 1 << 0,
+    DISPLAY_METRICS_WORK_AREA = 1 << 1,
+    DISPLAY_METRICS_DEVICE_SCALE_FACTOR = 1 << 2,
+    DISPLAY_METRICS_ROTATION = 1 << 3,

[oshima, 2014/05/20 01:03:02]

DISPLAY_METRIC_ (be consistent with enum type)

[mlamouri (slow - plz ping), 2014/05/20 12:52:58]

Done.

+  };
+  typedef uint8_t DisplayMetrics;

[oshima, 2014/05/20 01:03:02]

My preference is just to use uint32. unit32 is more common for bitmaps, and they
are so similar that people may mix up DisplayMetric and DisplayMetrics

[mlamouri (slow - plz ping), 2014/05/20 12:52:58]

I changed this but for the record, I would have preferred uint8_t because the
underlying type shouldn't matter here. Not worth dragging the review more though
because this patch is getting bit rotten quite quickly ;)

 
   // Called when |new_display| has been added.
   virtual void OnDisplayAdded(const Display& new_display) = 0;
@@ -24,6 +32,11 @@ class GFX_EXPORT DisplayObserver {
   // Called when |old_display| has been removed.
   virtual void OnDisplayRemoved(const Display& old_display) = 0;
 
+  // Called when a |display| has one or more metrics changed. |changed_metrics|
+  // will contain the information about the change, see |DisplayMetrics|.
+  virtual void OnDisplayMetricsChanged(const Display& display,
+                                       DisplayMetrics changed_metrics) = 0;
+
  protected:
   virtual ~DisplayObserver();
 };