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..dcbf9da60664a8e1372ccbfc8ac78180308dee2d 100644
--- a/components/exo/shell_surface.h
+++ b/components/exo/shell_surface.h
@@ -10,6 +10,7 @@
 #include <string>
 
 #include "ash/common/wm/window_state_observer.h"
+#include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "components/exo/surface_delegate.h"
@@ -147,6 +148,9 @@ 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);
@@ -216,6 +220,7 @@ class ShellSurface : public SurfaceDelegate,
  private:
   class ScopedConfigure;
   class ScopedAnimationsDisabled;
+  FRIEND_TEST_ALL_PREFIXES(ShellSurfaceTest, ShadowStartMaximized);

[reveman, 2016/08/01 16:19:23]

nit: it would be nice to not start poking into the private implementation
details in tests as when we have too much of that I think refactoring becomes
hard and turns into an exercise in rewriting tests instead rewriting
implementation logic..

can we test this shadow overlay logic in some other way? maybe check if the
bottom most child is opaque and the size of the shadow?

 
   // Surface state associated with each configure request.
   struct Config {
@@ -288,6 +293,7 @@ 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);
 };