Add HeadlessFocusClient to fix document.hasFocus() issues.

headless/lib/browser/headless_browser_impl_aura.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 "headless/lib/browser/headless_browser_impl.h"
 
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
+#include "headless/lib/browser/headless_focus_client.h"
 #include "headless/lib/browser/headless_screen.h"
+#include "ui/aura/client/focus_client.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window.h"
 #include "ui/display/screen.h"
 #include "ui/events/devices/device_data_manager.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace headless {
 
 void HeadlessBrowserImpl::PlatformInitialize() {
   HeadlessScreen* screen = HeadlessScreen::Create(options()->window_size);
   display::Screen::SetScreenInstance(screen);
 }
 
 void HeadlessBrowserImpl::PlatformCreateWindow() {
   DCHECK(aura::Env::GetInstance());
   ui::DeviceDataManager::CreateInstance();
 
   window_tree_host_.reset(
       new HeadlessWindowTreeHost(gfx::Rect(options()->window_size)));
   window_tree_host_->InitHost();
   window_tree_host_->window()->Show();
   window_tree_host_->SetParentWindow(window_tree_host_->window());
+
+  focus_client_.reset(new HeadlessFocusClient());
+  aura::client::SetFocusClient(window_tree_host_->window(),
+                               focus_client_.get());
 }
 
 void HeadlessBrowserImpl::PlatformInitializeWebContents(
     const gfx::Size& initial_size,
     content::WebContents* web_contents) {
   gfx::NativeView contents = web_contents->GetNativeView();
   gfx::NativeWindow parent_window = window_tree_host_->window();
   DCHECK(!parent_window->Contains(contents));
   parent_window->AddChild(contents);
   contents->Show();
   contents->SetBounds(gfx::Rect(initial_size));
 
   content::RenderWidgetHostView* host_view =
       web_contents->GetRenderWidgetHostView();
   if (host_view)
     host_view->SetSize(initial_size);
 }
 
 }  // namespace headless