Show corresponding window/widget/view in UIElement tree when clicking on a UI element.

components/ui_devtools/views/ui_devtools_unittest.cc

 // Copyright 2016 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 "base/memory/ptr_util.h"
 #include "base/strings/stringprintf.h"
 #include "components/ui_devtools/views/ui_devtools_css_agent.h"
 #include "components/ui_devtools/views/ui_devtools_dom_agent.h"
 #include "components/ui_devtools/views/ui_element.h"
 #include "components/ui_devtools/views/view_element.h"
@@ skipping 204 matching lines @@
     window->SetBounds(gfx::Rect());
     parent->AddChild(window.get());
     window->Show();
     return window;
   }
 
   void SetUp() override {
     fake_frontend_channel_ = base::MakeUnique<FakeFrontendChannel>();
     uber_dispatcher_ =
         base::MakeUnique<UberDispatcher>(fake_frontend_channel_.get());
-    dom_agent_ = base::MakeUnique<ui_devtools::UIDevToolsDOMAgent>();
+    dom_agent_ = base::MakeUnique<ui_devtools::UIDevToolsDOMAgent>(nullptr);
     dom_agent_->Init(uber_dispatcher_.get());
     css_agent_ =
         base::MakeUnique<ui_devtools::UIDevToolsCSSAgent>(dom_agent_.get());
     css_agent_->Init(uber_dispatcher_.get());
     css_agent_->enable();
 
     // We need to create |dom_agent| first to observe creation of
     // WindowTreeHosts in ViewTestBase::SetUp().
     views::ViewsTestBase::SetUp();
 
@@ skipping 636 matching lines @@
   SetStyleTexts(root_view_node, "\nheight: 73;\n  ", true);
   EXPECT_EQ(gfx::Rect(25, 35, 45, 73), root_view->bounds());
 
   SetStyleTexts(root_view_node, "\nx: 10; y: 23; width: 52;\nvisibility: 1;\n",
                 true);
   EXPECT_EQ(gfx::Rect(10, 23, 52, 73), root_view->bounds());
   EXPECT_TRUE(root_view->visible());
 }
 
 }  // namespace ui_devtools