Handle app custom icon via aura::Window property.

components/exo/shell_surface.h

Index: components/exo/shell_surface.h
diff --git a/components/exo/shell_surface.h b/components/exo/shell_surface.h
index d528f11ff73fa9c3b09ef834625cbd1be05f40a2..6991ccafe8a26263c07eeb3c2abae05806826b6e 100644
--- a/components/exo/shell_surface.h
+++ b/components/exo/shell_surface.h
@@ -140,9 +140,12 @@ class ShellSurface : public SurfaceDelegate,
   // Set whether the surface is always on top.
   void SetAlwaysOnTop(bool always_on_top);
 
-  // Set title for surface.
+  // Set title for the surface.
   void SetTitle(const base::string16& title);
 
+  // Set icon for the surface.
+  void SetIcon(const gfx::ImageSkia& icon);
+
   // Sets the system modality.
   void SetSystemModal(bool system_modal);
 
@@ -227,6 +230,7 @@ class ShellSurface : public SurfaceDelegate,
   bool CanMaximize() const override;
   bool CanMinimize() const override;
   base::string16 GetWindowTitle() const override;
+  gfx::ImageSkia GetWindowIcon() override;
   void SaveWindowPlacement(const gfx::Rect& bounds,
                            ui::WindowShowState show_state) override;
   bool GetSavedWindowPlacement(const views::Widget* widget,
@@ -373,6 +377,7 @@ class ShellSurface : public SurfaceDelegate,
   bool shadow_underlay_in_surface_ = true;
   bool pending_shadow_underlay_in_surface_ = true;
   bool system_modal_ = false;
+  gfx::ImageSkia icon_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellSurface);
 };