mus: Add debug key to print the server window hierarchy

components/mus/ws/window_manager_state.cc

Index: components/mus/ws/window_manager_state.cc
diff --git a/components/mus/ws/window_manager_state.cc b/components/mus/ws/window_manager_state.cc
index 681a52345687cd9536817f4c5dbb4ef4d18303b6..cb4e536ba4bf489cb54e6f0cfc159ebd5c17bcde 100644
--- a/components/mus/ws/window_manager_state.cc
+++ b/components/mus/ws/window_manager_state.cc
@@ -214,6 +214,8 @@ void WindowManagerState::Deactivate() {
 }
 
 void WindowManagerState::ProcessEvent(const ui::Event& event) {
+  RunDebugShortcuts(event);
+
   // If this is still waiting for an ack from a previously sent event, then
   // queue up the event to be dispatched once the ack is received.
   if (event_ack_timer_.IsRunning()) {
@@ -336,6 +338,20 @@ void WindowManagerState::DispatchInputEventToWindowImpl(
   tree->DispatchInputEvent(target, event);
 }
 
+void WindowManagerState::RunDebugShortcuts(const ui::Event& event) {

[msw, 2016/05/05 22:12:08]

Should this instead use accelerators, like ash/accelerators/debug_commands.h?
(even if it differs a bit, using accelerators seem more fitting here)

[James Cook, 2016/05/05 22:53:18]

It seems like overkill. Ash already has an accelerator registry, accelerator
dispatch code, etc. In mash, only the window manager has any of that, not the
window server. I doubt the window server itself will handle any shortcuts in
production. It seemed like overkill to build it just for debug stuff.

[msw, 2016/05/05 23:10:06]

See if it's easy to add an accelerator to the EventDispatcher for which this is
a delegate, and then handle it in OnAccelerator. If it's tough, this is fine.

+#if !defined(NDEBUG)
+  if (event.type() != ui::ET_KEY_PRESSED)
+    return;
+  const ui::KeyEvent* key = event.AsKeyEvent();
+  if (key->key_code() == ui::VKEY_S && key->IsControlDown()
+      && key->IsShiftDown() && key->IsAltDown()) {
+    // Error so it will be collected in system logs.
+    LOG(ERROR) << "ServerWindow hierarchy:\n"
+               << root()->GetDebugWindowHierarchy();
+  }
+#endif
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // EventDispatcherDelegate: