Add configuration_changed event and set_background_opacity request.

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 525e7c2fee40b82ce8d15fece2762262df08470b..c98c2ff2450caeef1877b88e3a416c009e65dc89 100644
--- a/components/exo/shell_surface.h
+++ b/components/exo/shell_surface.h
@@ -147,6 +147,9 @@ class ShellSurface : public SurfaceDelegate,
   // the shadow.
   void SetRectangularShadow(const gfx::Rect& content_bounds);
 
+  // Set the pacity of the background for the window that has a shadow.
+  void SetRectangularShadowBackgroundOpacity(float opacity);
+
   // Set scale factor for surface. The scale factor will be applied to surface
   // and all descendants.
   void SetScale(double scale);
@@ -213,6 +216,10 @@ class ShellSurface : public SurfaceDelegate,
   // Overridden from ui::AcceleratorTarget:
   bool AcceleratorPressed(const ui::Accelerator& accelerator) override;
 
+  const aura::Window* shadow_underlay_for_test() const {
+    return shadow_underlay_;
+  }
+
  private:
   class ScopedConfigure;
   class ScopedAnimationsDisabled;
@@ -288,6 +295,7 @@ class ShellSurface : public SurfaceDelegate,
   std::unique_ptr<ScopedAnimationsDisabled> scoped_animations_disabled_;
   int top_inset_height_ = 0;
   int pending_top_inset_height_ = 0;
+  float rectangular_shadow_background_opacity_ = 1.0;
 
   DISALLOW_COPY_AND_ASSIGN(ShellSurface);
 };