Remove docked windows entirely in M59.

ash/shell_unittest.cc

Index: ash/shell_unittest.cc
diff --git a/ash/shell_unittest.cc b/ash/shell_unittest.cc
index fe929cb67bebf1d3a8ca223a1d8697339b1d31fa..19ed1cad0d26e768ebc9f94c10121fcc64e9f15f 100644
--- a/ash/shell_unittest.cc
+++ b/ash/shell_unittest.cc
@@ -56,6 +56,11 @@ aura::Window* GetAlwaysOnTopContainer() {
 
 // Expect ALL the containers!
 void ExpectAllContainers() {
+  // Validate no duplicate container IDs.
+  std::set<int32_t> container_ids;
+  for (size_t i = 0; i < kAllShellContainerIdsSize; ++i)
+    EXPECT_TRUE(container_ids.insert(kAllShellContainerIds[i]).second);
+
   aura::Window* root_window = Shell::GetPrimaryRootWindow();
   EXPECT_TRUE(
       Shell::GetContainer(root_window, kShellWindowId_WallpaperContainer));