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..1c31de9734fd8b28a00c5748ec30d25ec6d7c6fe 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 window.

[reveman, 2017/06/01 18:28:42]

// Set icon for the surface.

and the function should not be a static function that takes a window. It's up to
the caller to get a shell surface instance and call this properly.

[khmel, 2017/06/01 21:55:46]

Done.

+  static void SetAppIcon(aura::Window* window, const gfx::ImageSkia& icon);

[reveman, 2017/06/01 18:02:23]

Why do we need shell surface API for this? Can we just set the icon properties
directly instead?
https://cs.chromium.org/chromium/src/ui/aura/client/aura_constants.cc?l=68

[khmel, 2017/06/01 18:08:20]

Widget uses WidgetDelegate to resolve the icon (and title). Default delegate
impl returns empty icon. In this case what we set can be removed. If we want
this way we have to prohibit to calling UpdateWindowIcon. 

[reveman, 2017/06/01 18:28:42]

Not sure this is called today for exo shell surface widgets but keeping an icon
member here in this class might still be the best approach so continuing review
of this patch.

[khmel, 2017/06/01 21:55:46]

Acknowledged.

+
   // 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);
 };