Implement "pinned" mode in ash.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 9d15218621caed7de0e2b2a5fbb747e93603d93b..9538c9d9b9a19f073dd8006df076cd0fb5d6fd98 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -75,6 +75,7 @@
 #include "ash/wm/overlay_event_filter.h"
 #include "ash/wm/overview/scoped_overview_animation_settings_factory_aura.h"
 #include "ash/wm/overview/window_selector_controller.h"
+#include "ash/wm/pinned_controller.h"
 #include "ash/wm/power_button_controller.h"
 #include "ash/wm/resize_shadow_controller.h"
 #include "ash/wm/system_gesture_event_filter.h"
@@ -791,6 +792,12 @@ Shell::~Shell() {
   lock_state_controller_.reset();
 
 #if defined(OS_CHROMEOS)
+  window_tree_host_manager_->RemoveObserver(pinned_controller_.get());
+  wm_shell_common_->RemoveShellObserver(pinned_controller_.get());
+  pinned_controller_.reset();
+#endif
+
+#if defined(OS_CHROMEOS)
   resolution_notification_controller_.reset();
 #endif
   desktop_background_controller_.reset();
@@ -1015,6 +1022,9 @@ void Shell::Init(const ShellInitParams& init_params) {
 
 #if defined(OS_CHROMEOS)
   sticky_keys_controller_.reset(new StickyKeysController);
+  pinned_controller_.reset(new wm::PinnedController);
+  wm_shell_common_->AddShellObserver(pinned_controller_.get());
+  window_tree_host_manager_->AddObserver(pinned_controller_.get());
 #endif
 
   lock_state_controller_.reset(new LockStateController);