[UiDevTools] Introduce new UiElement subclass to serve as the root of the DOM tree.

This is more prep for Mac support. The current root is a WindowElement which is
backed by aura::Window.

Bug: 769352
Change-Id: Ie7e05fb528f9f54fc07bc5ce96397715e0e34f1e
Reviewed-on: https://chromium-review.googlesource.com/876307
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537341}

components/ui_devtools/views/BUILD.gn

@@ -17,6 +17,8 @@ source_set("views") {
     "dom_agent.h",
     "overlay_agent.cc",
     "overlay_agent.h",
+    "root_element.cc",
+    "root_element.h",
     "ui_element.cc",
     "ui_element.h",
     "ui_element_delegate.h",

components/ui_devtools/views/dom_agent.cc

@@ -9,6 +9,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "components/ui_devtools/devtools_server.h"
 #include "components/ui_devtools/views/overlay_agent.h"
+#include "components/ui_devtools/views/root_element.h"
 #include "components/ui_devtools/views/ui_element.h"
 #include "components/ui_devtools/views/view_element.h"
 #include "components/ui_devtools/views/widget_element.h"
@@ -536,7 +537,7 @@ int DOMAgent::FindElementIdTargetedByPoint(
       views::Widget::GetWidgetForNativeWindow(targeted_window);
   if (!targeted_widget) {
 #if defined(USE_AURA)
-    return window_element_root_->FindUIElementIdForBackendElement<aura::Window>(
+    return element_root_->FindUIElementIdForBackendElement<aura::Window>(
         targeted_window);
 #else
     return 0;
@@ -554,7 +555,7 @@ int DOMAgent::FindElementIdTargetedByPoint(
   views::View* targeted_view =
       root_view->GetEventHandlerForPoint(point_in_targeted_window);
   DCHECK(targeted_view);
-  return window_element_root_->FindUIElementIdForBackendElement<views::View>(
+  return element_root_->FindUIElementIdForBackendElement<views::View>(
       targeted_view);
 }
 
@@ -607,7 +608,7 @@ void DOMAgent::ShowDistancesInHighlightOverlay(int pinned_id, int element_id) {
 int DOMAgent::GetParentIdOfNodeId(int node_id) const {
   DCHECK(node_id_to_ui_element_.count(node_id));
   const UIElement* element = node_id_to_ui_element_.at(node_id);
-  if (element->parent() && element->parent() != window_element_root_.get())
+  if (element->parent() && element->parent() != element_root_.get())
     return element->parent()->node_id();
   return 0;
 }
@@ -764,20 +765,17 @@ std::unique_ptr<DOM::Node> DOMAgent::BuildInitialTree() {
   is_building_tree_ = true;
   std::unique_ptr<Array<DOM::Node>> children = Array<DOM::Node>::create();
 
-  // TODO(thanhph): Root of UIElement tree shoudn't be WindowElement
-  // but maybe a new different element type.
-  window_element_root_ =
-      std::make_unique<WindowElement>(nullptr, this, nullptr);
+  element_root_ = base::MakeUnique<RootElement>(this);
 
   for (aura::Window* window : root_windows()) {
     UIElement* window_element =
-        new WindowElement(window, this, window_element_root_.get());
+        new WindowElement(window, this, element_root_.get());
 
     children->addItem(BuildTreeForUIElement(window_element));
-    window_element_root_->AddChild(window_element);
+    element_root_->AddChild(window_element);
   }
-  std::unique_ptr<DOM::Node> root_node = BuildNode(
-      "root", nullptr, std::move(children), window_element_root_->node_id());
+  std::unique_ptr<DOM::Node> root_node =
+      BuildNode("root", nullptr, std::move(children), element_root_->node_id());
   is_building_tree_ = false;
   return root_node;
 }
@@ -869,7 +867,7 @@ void DOMAgent::Reset() {
   is_building_tree_ = false;
   render_text_.reset();
   layer_for_highlighting_.reset();
-  window_element_root_.reset();
+  element_root_.reset();
   node_id_to_ui_element_.clear();
   observers_.Clear();
 }

components/ui_devtools/views/dom_agent.h

@@ -70,7 +70,7 @@ class DOMAgent : public UiDevToolsBaseAgent<protocol::DOM::Metainfo>,
   void AddObserver(DOMAgentObserver* observer);
   void RemoveObserver(DOMAgentObserver* observer);
   UIElement* GetElementFromNodeId(int node_id);
-  UIElement* window_element_root() const { return window_element_root_.get(); };
+  UIElement* element_root() const { return element_root_.get(); };
   const std::vector<gfx::NativeWindow>& root_windows() const {
     return root_windows_;
   };
@@ -127,7 +127,7 @@ class DOMAgent : public UiDevToolsBaseAgent<protocol::DOM::Metainfo>,
   bool show_size_on_canvas_ = false;
   HighlightRectsConfiguration highlight_rect_config_;
   bool is_swap_ = false;
-  std::unique_ptr<UIElement> window_element_root_;
+  std::unique_ptr<UIElement> element_root_;
   std::unordered_map<int, UIElement*> node_id_to_ui_element_;
 
   // TODO(thanhph): |layer_for_highlighting_| should be owned by the overlay

components/ui_devtools/views/overlay_agent.cc

@@ -45,7 +45,7 @@ protocol::Response OverlayAgent::hideHighlight() {
 void OverlayAgent::OnMouseEvent(ui::MouseEvent* event) {
   // Make sure the element tree has been populated before processing
   // mouse events.
-  if (!dom_agent_->window_element_root())
+  if (!dom_agent_->element_root())
     return;
 
   // Show parent of the pinned element with id |pinned_id_| when mouse scrolls
@@ -92,7 +92,7 @@ void OverlayAgent::OnMouseEvent(ui::MouseEvent* event) {
 }
 
 void OverlayAgent::OnKeyEvent(ui::KeyEvent* event) {
-  if (!dom_agent_->window_element_root())
+  if (!dom_agent_->element_root())
     return;
 
   // Exit inspect mode by pressing ESC key.

components/ui_devtools/views/root_element.cc

+// Copyright 2018 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 "components/ui_devtools/views/root_element.h"
+
+#include "components/ui_devtools/Protocol.h"
+#include "components/ui_devtools/views/ui_element_delegate.h"
+
+namespace ui_devtools {
+
+RootElement::RootElement(UIElementDelegate* ui_element_delegate)
+    : UIElement(UIElementType::ROOT, ui_element_delegate, nullptr) {}
+
+RootElement::~RootElement() {}
+
+std::vector<std::pair<std::string, std::string>>
+RootElement::GetCustomProperties() const {
+  NOTREACHED();
+  return {};
+}
+
+void RootElement::GetBounds(gfx::Rect* bounds) const {
+  NOTREACHED();
+}
+
+void RootElement::SetBounds(const gfx::Rect& bounds) {
+  NOTREACHED();
+}
+
+void RootElement::GetVisible(bool* visible) const {
+  NOTREACHED();
+}
+
+void RootElement::SetVisible(bool visible) {
+  NOTREACHED();
+}
+std::unique_ptr<protocol::Array<std::string>> RootElement::GetAttributes()
+    const {
+  NOTREACHED();
+  return nullptr;
+}
+
+std::pair<gfx::NativeWindow, gfx::Rect> RootElement::GetNodeWindowAndBounds()
+    const {
+  NOTREACHED();
+  return {};
+}
+
+}  // namespace ui_devtools

components/ui_devtools/views/root_element.h

+// Copyright 2018 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.
+
+#ifndef COMPONENTS_UI_DEVTOOLS_VIEWS_ROOT_ELEMENT_H_
+#define COMPONENTS_UI_DEVTOOLS_VIEWS_ROOT_ELEMENT_H_
+
+#include "base/macros.h"
+#include "components/ui_devtools/views/ui_element.h"
+
+namespace ui_devtools {
+
+class RootElement : public UIElement {
+ public:
+  explicit RootElement(UIElementDelegate* ui_element_delegate);
+  ~RootElement() override;
+
+  // UIElement:
+  std::vector<std::pair<std::string, std::string>> GetCustomProperties()
+      const override;
+  void GetBounds(gfx::Rect* bounds) const override;
+  void SetBounds(const gfx::Rect& bounds) override;
+  void GetVisible(bool* visible) const override;
+  void SetVisible(bool visible) override;
+  std::unique_ptr<protocol::Array<std::string>> GetAttributes() const override;
+  std::pair<gfx::NativeWindow, gfx::Rect> GetNodeWindowAndBounds()
+      const override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(RootElement);
+};
+}  // namespace ui_devtools
+
+#endif  // COMPONENTS_UI_DEVTOOLS_VIEWS_ROOT_ELEMENT_H_

components/ui_devtools/views/ui_element.cc

@@ -27,6 +27,8 @@ UIElement::~UIElement() {
 
 std::string UIElement::GetTypeName() const {
   switch (type_) {
+    case UIElementType::ROOT:
+      return "Root";
     case UIElementType::WINDOW:
       return "Window";
     case UIElementType::WIDGET:

components/ui_devtools/views/ui_element.h

@@ -22,7 +22,7 @@ class Array;
 }
 
 // UIElement type.
-enum UIElementType { WINDOW, WIDGET, VIEW };
+enum UIElementType { WINDOW, WIDGET, VIEW, ROOT };
 
 class UIElement {
  public: