Exclude Android system windows from a voice interaction snapshsot.

chrome/browser/chromeos/arc/voice_interaction/arc_voice_interaction_framework_service.cc

 // Copyright 2017 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 "chrome/browser/chromeos/arc/voice_interaction/arc_voice_interaction_framework_service.h"
 
 #include <utility>
 #include <vector>
 
 #include "ash/accelerators/accelerator_controller.h"
+#include "ash/public/cpp/shell_window_ids.h"
 #include "ash/shell.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/containers/flat_set.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/task_scheduler/post_task.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/browser_window.h"
@@ skipping 31 matching lines @@
 
 std::unique_ptr<ui::LayerTreeOwner> CreateLayerTreeForSnapshot(
     aura::Window* root_window) {
   using LayerSet = base::flat_set<const ui::Layer*>;
   LayerSet blocked_layers;
   for (auto* browser : *BrowserList::GetInstance()) {
     if (browser->profile()->IsOffTheRecord())
       blocked_layers.insert(browser->window()->GetNativeWindow()->layer());
   }
 
+  LayerSet excluded_layers;
+  // For the best UX the metalayer has to be excluded from the snapshot.
+  // It is currently impossible to identify the metalayer among others layers
+  // under kShellWindowId_SystemModalContainer. Other layers in this container
+  // are not relevant for this kind of snapshot, so it is safe to exclude all
+  // of them.
+  aura::Window* modal_container = ash::Shell::GetContainer(
+      root_window, ash::kShellWindowId_SystemModalContainer);

[xc, 2017/05/19 00:10:42]

Why metalayer view is in this container?

[kaznacheev, 2017/05/19 00:31:05]

This is where Chrome puts all Android system windows (that is, windows with null
application token).

+  if (modal_container != nullptr) {

[Luis Héctor Chávez, 2017/05/19 15:03:21]

nit: elide braces. Same in L91.

[Vladislav Kaznacheev, 2017/05/19 17:11:20]

Done.

+    excluded_layers.insert(modal_container->layer());
+  }
+
   auto layer_tree_owner = ::wm::RecreateLayersWithClosure(
       root_window, base::BindRepeating(
-                       [](LayerSet blocked_layers,
+                       [](LayerSet blocked_layers, LayerSet excluded_layers,
                           ui::LayerOwner* owner) -> std::unique_ptr<ui::Layer> {
                          // Parent layer is excluded meaning that it's pointless
                          // to clone current child and all its descendants. This
                          // reduces the number of layers to create.
                          if (blocked_layers.count(owner->layer()->parent()))
                            return nullptr;
                          if (blocked_layers.count(owner->layer())) {
                            auto layer = base::MakeUnique<ui::Layer>(
                                ui::LayerType::LAYER_SOLID_COLOR);
                            layer->SetBounds(owner->layer()->bounds());
                            layer->SetColor(SK_ColorBLACK);
                            return layer;
                          }
+                         if (excluded_layers.count(owner->layer())) {
+                           return nullptr;
+                         }
                          return owner->RecreateLayer();
                        },
-                       std::move(blocked_layers)));
+                       std::move(blocked_layers), std::move(excluded_layers)));
 
   // layer_tree_owner cannot be null since we are starting off from the root
   // window, which could never be incognito.
   DCHECK(layer_tree_owner);
 
   auto* root_layer = layer_tree_owner->root();
   root_window->layer()->Add(root_layer);
   root_window->layer()->StackAtBottom(root_layer);
   return layer_tree_owner;
 }
@@ skipping 171 matching lines @@
           SetMetalayerVisibility);
   if (!framework_instance) {
     if (!metalayer_closed_callback_.is_null())
       base::ResetAndReturn(&metalayer_closed_callback_).Run();
     return;
   }
   framework_instance->SetMetalayerVisibility(visible);
 }
 
 }  // namespace arc