Makes WorkspaceLayoutManager use ash/wm/common types

ash/wm/common/fullscreen_window_finder.cc

Index: ash/wm/common/fullscreen_window_finder.cc
diff --git a/ash/wm/common/fullscreen_window_finder.cc b/ash/wm/common/fullscreen_window_finder.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f817cc73e14d2d0e11827b3744e8b7d9e6eac433
--- /dev/null
+++ b/ash/wm/common/fullscreen_window_finder.cc
@@ -0,0 +1,53 @@
+// Copyright 2016 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 "ash/wm/common/fullscreen_window_finder.h"
+
+#include "ash/wm/common/switchable_windows.h"
+#include "ash/wm/common/window_state.h"
+#include "ash/wm/common/wm_globals.h"
+#include "ash/wm/common/wm_shell_window_ids.h"
+#include "ash/wm/common/wm_window.h"
+#include "ui/compositor/layer.h"
+
+namespace ash {
+namespace wm {
+
+WmWindow* GetWindowForFullscreenMode(WmWindow* context) {
+  WmWindow* topmost_window = nullptr;
+  WmWindow* active_window = context->GetGlobals()->GetActiveWindow();
+  if (active_window &&
+      active_window->GetRootWindow() == context->GetRootWindow() &&
+      IsSwitchableContainer(active_window->GetParent())) {
+    // Use the active window when it is on the current root window to determine
+    // the fullscreen state to allow temporarily using a panel or docked window
+    // (which are always above the default container) while a fullscreen
+    // window is open. We only use the active window when in a switchable
+    // container as the launcher should not exit fullscreen mode.
+    topmost_window = active_window;
+  } else {
+    // Otherwise, use the topmost window on the root window's default container
+    // when there is no active window on this root window.
+    std::vector<WmWindow*> windows =
+        context->GetRootWindow()
+            ->GetChildByShellWindowId(kShellWindowId_DefaultContainer)
+            ->GetChildren();
+    for (auto iter = windows.rbegin(); iter != windows.rend(); ++iter) {
+      if ((*iter)->GetWindowState()->IsUserPositionable() &&
+          (*iter)->GetLayer()->GetTargetVisibility()) {
+        topmost_window = *iter;
+        break;
+      }
+    }
+  }
+  while (topmost_window) {
+    if (topmost_window->GetWindowState()->IsFullscreen())
+      return topmost_window;
+    topmost_window = topmost_window->GetTransientParent();
+  }
+  return nullptr;
+}
+
+}  // namespace wm
+}  // namespace ash