Revert of [headless] Use individual aura::WindowTreeHosts per WebContents.

headless/lib/browser/headless_browser_impl_aura.cc

Index: headless/lib/browser/headless_browser_impl_aura.cc
diff --git a/headless/lib/browser/headless_browser_impl_aura.cc b/headless/lib/browser/headless_browser_impl_aura.cc
index 57a0f77c7918b6bcfd7df9277934a221dc564897..33b028a41fe64a7c7ec3e3277444770cac5f2243 100644
--- a/headless/lib/browser/headless_browser_impl_aura.cc
+++ b/headless/lib/browser/headless_browser_impl_aura.cc
@@ -7,7 +7,9 @@
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
 #include "headless/lib/browser/headless_clipboard.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/base/clipboard/clipboard.h"
@@ -21,8 +23,6 @@
   HeadlessScreen* screen = HeadlessScreen::Create(options()->window_size);
   display::Screen::SetScreenInstance(screen);
 
-  // TODO(eseckler): We shouldn't share clipboard contents across WebContents
-  // (or at least BrowserContexts).
   ui::Clipboard::SetClipboardForCurrentThread(
       base::MakeUnique<HeadlessClipboard>());
 }
@@ -30,29 +30,30 @@
 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,
-    HeadlessWebContentsImpl* web_contents) {
-  gfx::Rect initial_rect(initial_size);
-
-  auto window_tree_host =
-      base::MakeUnique<HeadlessWindowTreeHost>(initial_rect);
-  window_tree_host->InitHost();
-  gfx::NativeWindow parent_window = window_tree_host->window();
-  parent_window->Show();
-  window_tree_host->SetParentWindow(parent_window);
-  web_contents->set_window_tree_host(std::move(window_tree_host));
-
-  gfx::NativeView contents = web_contents->web_contents()->GetNativeView();
+    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(initial_rect);
+  contents->SetBounds(gfx::Rect(initial_size));
 
   content::RenderWidgetHostView* host_view =
-      web_contents->web_contents()->GetRenderWidgetHostView();
+      web_contents->GetRenderWidgetHostView();
   if (host_view)
     host_view->SetSize(initial_size);
 }