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..b8d6d420bd47db3045f84ce5f4abedebeb2412b6 100644
--- a/components/exo/shell_surface.h
+++ b/components/exo/shell_surface.h
@@ -154,6 +154,9 @@ class ShellSurface : public SurfaceDelegate,
   // Set the application ID for the surface.
   void SetApplicationId(const std::string& application_id);
 
+  // Set icon for the surface.
+  void SetAppIcon(const gfx::ImageSkia& icon);

[reveman, 2017/06/01 22:05:36]

nit: SetIcon or SetApplicationIcon as we're not using the App abbreviation
above. I prefer SetIcon as it's consistent with SetTitle.

[khmel, 2017/06/01 22:19:27]

Done.

+
   // Start an interactive move of surface.
   void Move();
 
@@ -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);
 };