Register the window in MaximizeModeWindowManager when the window is shown.

ash/common/wm/maximize_mode/maximize_mode_window_manager.cc

 // Copyright 2014 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/common/wm/maximize_mode/maximize_mode_window_manager.h"
 
 #include "ash/common/ash_switches.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/wm/maximize_mode/maximize_mode_event_handler.h"
@@ skipping 81 matching lines @@
   backdrops_hidden_ = false;
   EnableBackdropBehindTopWindowOnEachDisplay(true);
   SetDeferBoundsUpdates(false);
 }
 
 void MaximizeModeWindowManager::OnWindowDestroying(WmWindow* window) {
   if (IsContainerWindow(window)) {
     // container window can be removed on display destruction.
     window->RemoveObserver(this);
     observed_container_windows_.erase(window);
+  } else if (base::ContainsValue(added_windows_, window)) {
+    // Added window was destroyed before being shown.
+    added_windows_.erase(window);
+    window->RemoveObserver(this);
   } else {
     // If a known window gets destroyed we need to remove all knowledge about
     // it.
     ForgetWindow(window);
   }
 }
 
 void MaximizeModeWindowManager::OnWindowTreeChanged(
     WmWindow* window,
     const TreeChangeParams& params) {
   // A window can get removed and then re-added by a drag and drop operation.
   if (params.new_parent && IsContainerWindow(params.new_parent) &&
       !base::ContainsKey(window_state_map_, params.target)) {
+    // Wait until the window become visible because the client
+    // may update the flag to control if the window should be added.
+    if (!params.target->IsVisible()) {

[Mr4D (OOO till 08-26), 2016/08/18 01:45:45]

This is confusing. You mention "wait until the window becomes visible" but then
if (!...isVisible()).

Maybe you should write:
If the window is invisible we do .. since the client may update ..?

[oshima, 2016/08/18 04:26:09]

Updated to:

    // Don't register the window if the window is invisible. Instead,
    // wait until it becomes visible because the client may update the
    // flag to control if the window should be added.

+      if (!base::ContainsValue(added_windows_, params.target)) {
+        added_windows_.insert(params.target);
+        params.target->AddObserver(this);
+      }
+      return;
+    }
     MaximizeAndTrackWindow(params.target);
     // When the state got added, the "WM_EVENT_ADDED_TO_WORKSPACE" event got
     // already sent and we have to notify our state again.
     if (base::ContainsKey(window_state_map_, params.target)) {
       wm::WMEvent event(wm::WM_EVENT_ADDED_TO_WORKSPACE);
       params.target->GetWindowState()->OnWMEvent(&event);
     }
   }
 }
 
 void MaximizeModeWindowManager::OnWindowPropertyChanged(
     WmWindow* window,
     WmWindowProperty property) {
   // Stop managing |window| if the always-on-top property is added.
   if (property == WmWindowProperty::ALWAYS_ON_TOP && window->IsAlwaysOnTop())
     ForgetWindow(window);
 }
 
 void MaximizeModeWindowManager::OnWindowBoundsChanged(
     WmWindow* window,
     const gfx::Rect& old_bounds,
     const gfx::Rect& new_bounds) {
   if (!IsContainerWindow(window))
     return;
   // Reposition all non maximizeable windows.
   for (auto& pair : window_state_map_)
     pair.second->UpdateWindowPosition(pair.first->GetWindowState());
 }
 
+void MaximizeModeWindowManager::OnWindowVisibilityChanged(WmWindow* window,
+                                                          bool visible) {
+  // Skip if it's already managed.
+  if (base::ContainsKey(window_state_map_, window))
+    return;
+
+  if (IsContainerWindow(window->GetParent()) &&
+      base::ContainsValue(added_windows_, window) && visible) {
+    added_windows_.erase(window);
+    window->RemoveObserver(this);
+    MaximizeAndTrackWindow(window);
+    // When the state got added, the "WM_EVENT_ADDED_TO_WORKSPACE" event got
+    // already sent and we have to notify our state again.
+    if (base::ContainsKey(window_state_map_, window)) {
+      wm::WMEvent event(wm::WM_EVENT_ADDED_TO_WORKSPACE);
+      window->GetWindowState()->OnWMEvent(&event);
+    }

[Mr4D (OOO till 08-26), 2016/08/18 01:45:45]

Could you put line 167-173 into a function and call that from here and from line
128?

[oshima, 2016/08/18 04:26:09]

I believe we can move the added to workspace to MaximizeAndTrackWindow, but let
me do it in a separate CL because this has to be merged to m53.

+  }
+}
+
 void MaximizeModeWindowManager::OnDisplayAdded(
     const display::Display& display) {
   DisplayConfigurationChanged();
 }
 
 void MaximizeModeWindowManager::OnDisplayRemoved(
     const display::Display& display) {
   DisplayConfigurationChanged();
 }
 
@@ skipping 128 matching lines @@
   for (WmWindow* root : WmShell::Get()->GetAllRootWindows()) {
     WmRootWindowController* controller = root->GetRootWindowController();
     WmWindow* default_container =
         root->GetChildByShellWindowId(kShellWindowId_DefaultContainer);
     controller->SetMaximizeBackdropDelegate(base::WrapUnique(
         enable ? new WorkspaceBackdropDelegate(default_container) : nullptr));
   }
 }
 
 }  // namespace ash