Implement "pinned" mode in ash.

ash/wm/workspace/workspace_layout_manager_unittest.cc

Index: ash/wm/workspace/workspace_layout_manager_unittest.cc
diff --git a/ash/wm/workspace/workspace_layout_manager_unittest.cc b/ash/wm/workspace/workspace_layout_manager_unittest.cc
index aab232016ce6b1e2eb7d925478b8ef368683d7b8..1331522b0ea804f3719e74e1a45fd0b21d4aa211 100644
--- a/ash/wm/workspace/workspace_layout_manager_unittest.cc
+++ b/ash/wm/workspace/workspace_layout_manager_unittest.cc
@@ -676,6 +676,30 @@ TEST_F(WorkspaceLayoutManagerSoloTest, FullscreenSuspendsAlwaysOnTop) {
                          ->GetWindowForFullscreenMode());
 }
 
+// Similary, pinned window causes always_on_top_ windows to stack below.
+TEST_F(WorkspaceLayoutManagerSoloTest, PinnedSuspendsAlwaysOnTop) {
+  gfx::Rect bounds(100, 100, 200, 200);
+  std::unique_ptr<aura::Window> pinned_window(CreateTestWindow(bounds));
+  std::unique_ptr<aura::Window> always_on_top_window1(CreateTestWindow(bounds));
+  std::unique_ptr<aura::Window> always_on_top_window2(CreateTestWindow(bounds));
+  always_on_top_window1->SetProperty(aura::client::kAlwaysOnTopKey, true);
+  always_on_top_window2->SetProperty(aura::client::kAlwaysOnTopKey, true);
+
+  // Making a window pinned temporarily suspends always on top state.
+  wm::PinWindow(pinned_window.get());
+  EXPECT_FALSE(
+      always_on_top_window1->GetProperty(aura::client::kAlwaysOnTopKey));
+  EXPECT_FALSE(
+      always_on_top_window2->GetProperty(aura::client::kAlwaysOnTopKey));
+
+  // Making pinned window normal restores always on top windows.
+  WmWindowAura::Get(pinned_window.get())->GetWindowState()->Restore();
+  EXPECT_TRUE(
+      always_on_top_window1->GetProperty(aura::client::kAlwaysOnTopKey));
+  EXPECT_TRUE(
+      always_on_top_window2->GetProperty(aura::client::kAlwaysOnTopKey));
+}
+
 // Tests fullscreen window size during root window resize.
 TEST_F(WorkspaceLayoutManagerSoloTest, FullscreenRootWindowResize) {
   gfx::Rect bounds(100, 100, 200, 200);