Enable ash window cycle UI by default.

ash/common/wm/window_cycle_controller.cc

Index: ash/common/wm/window_cycle_controller.cc
diff --git a/ash/common/wm/window_cycle_controller.cc b/ash/common/wm/window_cycle_controller.cc
index 6135f600aa34ceb59e4e0db89ed6bcd3abe0e9b7..bf2b5471ec6cf845f99be02b64617bbb7cdbb52e 100644
--- a/ash/common/wm/window_cycle_controller.cc
+++ b/ash/common/wm/window_cycle_controller.cc
@@ -6,10 +6,12 @@
 
 #include "ash/common/metrics/task_switch_source.h"
 #include "ash/common/session/session_state_delegate.h"
+#include "ash/common/shell_window_ids.h"
 #include "ash/common/wm/mru_window_tracker.h"
 #include "ash/common/wm/window_cycle_event_filter.h"
 #include "ash/common/wm/window_cycle_list.h"
 #include "ash/common/wm_shell.h"
+#include "ash/common/wm_window.h"
 #include "base/metrics/histogram.h"
 
 namespace ash {
@@ -52,6 +54,21 @@ void WindowCycleController::HandleCycleWindow(Direction direction) {
 void WindowCycleController::StartCycling() {
   MruWindowTracker::WindowList window_list =
       WmShell::Get()->mru_window_tracker()->BuildMruWindowList();
+  // Exclude the AppList window, which will hide as soon as cycling starts
+  // anyway. It doesn't make sense to count it as a "switchable" window, yet
+  // a lot of code relies on the MRU list returning the app window. If we
+  // don't manually do this, the window cycling UI won't crash or misbehave, but
+  // there will be a flicker as the target window changes.

[Evan Stade, 2016/08/12 22:51:57]

this is really annoying and gross. See ash/common/wm/switchable_windows.{cc,h}.
In particular, the shelf's hide/show state depends on me not changing the
definition of "switchable" windows, even though the current definition is very
deceptive. There may be other places not covered by unit tests that also rely on
the app list being included in this window list as a lot of places seem to use
the MRU list.

+  window_list.erase(
+      std::remove_if(window_list.begin(), window_list.end(),
+                     [](WmWindow* window) {
+                       bool foo = window->GetRootWindow()
+                                      ->GetChildByShellWindowId(
+                                          kShellWindowId_AppListContainer)
+                                      ->Contains(window);
+                       return foo;
+                     }),
+      window_list.end());
 
   active_window_before_window_cycle_ = GetActiveWindow(window_list);