aura: Draw drop shadows under browsers and menus.

ui/aura_shell/shell.cc

Index: ui/aura_shell/shell.cc
diff --git a/ui/aura_shell/shell.cc b/ui/aura_shell/shell.cc
index b439de1090e7a796cb25e534e0c157144f6378b3..8a63f21b52153ea72cc7a26625eee67300b76ef5 100644
--- a/ui/aura_shell/shell.cc
+++ b/ui/aura_shell/shell.cc
@@ -19,6 +19,7 @@
 #include "ui/aura_shell/drag_drop_controller.h"
 #include "ui/aura_shell/launcher/launcher.h"
 #include "ui/aura_shell/modal_container_layout_manager.h"
+#include "ui/aura_shell/shadow_controller.h"
 #include "ui/aura_shell/shelf_layout_controller.h"
 #include "ui/aura_shell/shell_delegate.h"
 #include "ui/aura_shell/shell_factory.h"
@@ -172,9 +173,11 @@ void Shell::Init() {
 
   shelf_layout_controller_.reset(new internal::ShelfLayoutController(
       launcher_->widget(), status_widget));
-
   desktop_layout->set_shelf(shelf_layout_controller_.get());
 
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(switches::kAuraNoShadows))
+    shadow_controller_.reset(new internal::ShadowController());
+
   if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kAuraWindows)) {
     EnableWorkspaceManager();
   } else {
@@ -187,7 +190,6 @@ void Shell::Init() {
   // Force a layout.
   desktop_layout->OnWindowResized();
 
-  // Initialize drag drop controller.
   drag_drop_controller_.reset(new internal::DragDropController);
   aura::Desktop::GetInstance()->SetProperty(aura::kDesktopDragDropClientKey,
       static_cast<aura::DragDropClient*>(drag_drop_controller_.get()));