Create a visible shelf and constrain window movement

ui/aura_shell/toplevel_layout_manager.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/aura_shell/toplevel_layout_manager.h"
 
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/window.h"
 #include "ui/aura_shell/property_util.h"
 #include "ui/aura_shell/shelf_layout_manager.h"
@@ skipping 30 matching lines @@
   UpdateShelfVisibility();
 }
 
 void ToplevelLayoutManager::OnChildWindowVisibilityChanged(aura::Window* child,
                                                            bool visibile) {
   UpdateShelfVisibility();
 }
 
 void ToplevelLayoutManager::SetChildBounds(aura::Window* child,
                                            const gfx::Rect& requested_bounds) {
-  SetChildBoundsDirect(child, requested_bounds);
+  const static int kTitleHeight = 12;
+  gfx::Rect child_bounds(requested_bounds);
+  gfx::Rect work_area = gfx::Screen::GetMonitorWorkAreaNearestWindow(child);
+  if (child_bounds.y() < 0)
+    child_bounds.set_y(0);
+  else if (child_bounds.y() + kTitleHeight > work_area.bottom())
+    child_bounds.set_y(work_area.bottom() - kTitleHeight);
+  SetChildBoundsDirect(child, child_bounds);
 }
 
 void ToplevelLayoutManager::OnWindowPropertyChanged(aura::Window* window,
                                                     const char* name,
                                                     void* old) {
   if (name == aura::kShowStateKey)
     WindowStateChanged(window);
 }
 
 void ToplevelLayoutManager::WindowStateChanged(aura::Window* window) {
@@ skipping 34 matching lines @@
         ui::SHOW_STATE_FULLSCREEN) {
       has_fullscreen_window = true;
       break;
     }
   }
   shelf_->SetVisible(!has_fullscreen_window);
 }
 
 }  // namespace internal
 }  // namespace aura_shell