Aura: Switch window mode when screen resolution changes

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 16add64ab50f47014fc13803f5be4f8f8518fe7a..f1d92bd3dd3fc02f760c0434e337d992c6ca8911 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -15,6 +15,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
+#include "ui/aura/root_window_observer.h"
 
 class CommandLine;
 
@@ -62,7 +63,7 @@ class WorkspaceController;
 //
 // Upon creation, the Shell sets itself as the RootWindow's delegate, which
 // takes ownership of the Shell.
-class ASH_EXPORT Shell {
+class ASH_EXPORT Shell : public aura::RootWindowObserver {
  public:
   // In compact window mode we fill the screen with a single maximized window,
   // similar to ChromeOS R17 and earlier.  In overlapping mode we have draggable
@@ -140,6 +141,9 @@ class ASH_EXPORT Shell {
     return shadow_controller_.get();
   }
 
+  // aura::RootWindowObserver overrides:
+  virtual void OnRootWindowResized(const gfx::Size& new_size) OVERRIDE;
+
  private:
   FRIEND_TEST_ALL_PREFIXES(ShellTest, ComputeWindowMode);
   FRIEND_TEST_ALL_PREFIXES(ShellTest, ChangeWindowMode);