Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

35 files changed, 1835 insertions, 0 deletions

diff --git a/devtools/client/dom/.eslintrc.js b/devtools/client/dom/.eslintrc.js
new file mode 100644
index 0000000000..8e2ca9a042
--- /dev/null
+++ b/devtools/client/dom/.eslintrc.js
@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+module.exports = {
+  globals: {
+    XMLHttpRequest: true,
+    window: true,
+    define: true,
+    addEventListener: true,
+    document: true,
+    dispatchEvent: true,
+    MessageEvent: true,
+  },
+};
diff --git a/devtools/client/dom/content/actions/filter.js b/devtools/client/dom/content/actions/filter.js
new file mode 100644
index 0000000000..83de5a95ce
--- /dev/null
+++ b/devtools/client/dom/content/actions/filter.js
@@ -0,0 +1,19 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const constants = require("devtools/client/dom/content/constants");
+
+/**
+ * Used to filter DOM panel content.
+ */
+function setVisibilityFilter(filter) {
+  return {
+    filter: filter,
+    type: constants.SET_VISIBILITY_FILTER,
+  };
+}
+
+// Exports from this module
+exports.setVisibilityFilter = setVisibilityFilter;
diff --git a/devtools/client/dom/content/actions/grips.js b/devtools/client/dom/content/actions/grips.js
new file mode 100644
index 0000000000..a49f01f566
--- /dev/null
+++ b/devtools/client/dom/content/actions/grips.js
@@ -0,0 +1,54 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* globals DomProvider */
+"use strict";
+
+const constants = require("devtools/client/dom/content/constants");
+
+/**
+ * Used to fetch grip prototype and properties from the backend.
+ */
+function requestProperties(grip) {
+  return {
+    grip: grip,
+    type: constants.FETCH_PROPERTIES,
+    status: "start",
+    error: false,
+  };
+}
+
+/**
+ * Executed when grip properties are received from the backend.
+ */
+function receiveProperties(grip, response, error) {
+  return {
+    grip: grip,
+    type: constants.FETCH_PROPERTIES,
+    status: "end",
+    response: response,
+    error: error,
+  };
+}
+
+/**
+ * Used to get properties from the backend and fire an action
+ * when they are received.
+ */
+function fetchProperties(grip) {
+  return async ({ dispatch }) => {
+    try {
+      // Use 'DomProvider' object exposed from the chrome scope.
+      const response = await DomProvider.getPrototypeAndProperties(grip);
+      dispatch(receiveProperties(grip, response));
+    } catch (e) {
+      console.error("Error while fetching properties", e);
+    }
+    DomProvider.onPropertiesFetched();
+  };
+}
+
+// Exports from this module
+exports.requestProperties = requestProperties;
+exports.receiveProperties = receiveProperties;
+exports.fetchProperties = fetchProperties;
diff --git a/devtools/client/dom/content/actions/moz.build b/devtools/client/dom/content/actions/moz.build
new file mode 100644
index 0000000000..8c1c56d39a
--- /dev/null
+++ b/devtools/client/dom/content/actions/moz.build
@@ -0,0 +1,9 @@
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "filter.js",
+    "grips.js",
+)
diff --git a/devtools/client/dom/content/components/DomTree.js b/devtools/client/dom/content/components/DomTree.js
new file mode 100644
index 0000000000..88faa6f2a8
--- /dev/null
+++ b/devtools/client/dom/content/components/DomTree.js
@@ -0,0 +1,132 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* global DomProvider */
+
+"use strict";
+
+// React & Redux
+const {
+  Component,
+  createFactory,
+} = require("devtools/client/shared/vendor/react");
+const PropTypes = require("devtools/client/shared/vendor/react-prop-types");
+
+const { connect } = require("devtools/client/shared/vendor/react-redux");
+
+const TreeView = createFactory(
+  require("devtools/client/shared/components/tree/TreeView")
+);
+// Reps
+const { REPS, MODE } = require("devtools/client/shared/components/reps/index");
+const { Rep } = REPS;
+
+const Grip = REPS.Grip;
+// DOM Panel
+const { GripProvider } = require("devtools/client/dom/content/grip-provider");
+
+const { DomDecorator } = require("devtools/client/dom/content/dom-decorator");
+
+/**
+ * Renders DOM panel tree.
+ */
+class DomTree extends Component {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      filter: PropTypes.string,
+      grips: PropTypes.object,
+      object: PropTypes.any,
+      openLink: PropTypes.func,
+    };
+  }
+
+  constructor(props) {
+    super(props);
+    this.onFilter = this.onFilter.bind(this);
+  }
+
+  /**
+   * Filter DOM properties. Return true if the object
+   * should be visible in the tree.
+   */
+  onFilter(object) {
+    if (!this.props.filter) {
+      return true;
+    }
+
+    return object.name && object.name.indexOf(this.props.filter) > -1;
+  }
+
+  /**
+   * Render DOM panel content
+   */
+  render() {
+    const { dispatch, grips, object, openLink } = this.props;
+
+    const columns = [
+      {
+        id: "value",
+      },
+    ];
+
+    let onDOMNodeMouseOver;
+    let onDOMNodeMouseOut;
+    let onInspectIconClick;
+    const toolbox = DomProvider.getToolbox();
+    if (toolbox) {
+      const highlighter = toolbox.getHighlighter();
+      onDOMNodeMouseOver = async (grip, options = {}) => {
+        return highlighter.highlight(grip, options);
+      };
+      onDOMNodeMouseOut = async () => {
+        return highlighter.unhighlight();
+      };
+      onInspectIconClick = async grip => {
+        return toolbox.viewElementInInspector(grip, "inspect_dom");
+      };
+    }
+
+    // This is the integration point with Reps. The DomTree is using
+    // Reps to render all values. The code also specifies default rep
+    // used for data types that don't have its own specific template.
+    const renderValue = props => {
+      const repProps = Object.assign({}, props, {
+        onDOMNodeMouseOver,
+        onDOMNodeMouseOut,
+        onInspectIconClick,
+        defaultRep: Grip,
+        cropLimit: 50,
+      });
+
+      // Object can be an objectFront, while Rep always expect grips.
+      if (props?.object?.getGrip) {
+        repProps.object = props.object.getGrip();
+      }
+
+      return Rep(repProps);
+    };
+
+    return TreeView({
+      columns,
+      decorator: new DomDecorator(),
+      mode: MODE.SHORT,
+      object,
+      onFilter: this.onFilter,
+      openLink,
+      provider: new GripProvider(grips, dispatch),
+      renderValue,
+    });
+  }
+}
+
+const mapStateToProps = state => {
+  return {
+    grips: state.grips,
+    filter: state.filter,
+  };
+};
+
+// Exports from this module
+module.exports = connect(mapStateToProps)(DomTree);
diff --git a/devtools/client/dom/content/components/MainFrame.js b/devtools/client/dom/content/components/MainFrame.js
new file mode 100644
index 0000000000..16aee4856e
--- /dev/null
+++ b/devtools/client/dom/content/components/MainFrame.js
@@ -0,0 +1,74 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* globals DomProvider */
+
+"use strict";
+
+// React & Redux
+const {
+  Component,
+  createFactory,
+} = require("devtools/client/shared/vendor/react");
+const dom = require("devtools/client/shared/vendor/react-dom-factories");
+const PropTypes = require("devtools/client/shared/vendor/react-prop-types");
+
+const { connect } = require("devtools/client/shared/vendor/react-redux");
+// DOM Panel
+const DomTree = createFactory(
+  require("devtools/client/dom/content/components/DomTree")
+);
+
+const MainToolbar = createFactory(
+  require("devtools/client/dom/content/components/MainToolbar")
+);
+// Shortcuts
+const { div } = dom;
+
+/**
+ * Renders basic layout of the DOM panel. The DOM panel content consists
+ * from two main parts: toolbar and tree.
+ */
+class MainFrame extends Component {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      filter: PropTypes.string,
+      object: PropTypes.any,
+    };
+  }
+
+  /**
+   * Render DOM panel content
+   */
+  render() {
+    const { filter, object } = this.props;
+
+    return div(
+      { className: "mainFrame" },
+      MainToolbar({
+        dispatch: this.props.dispatch,
+        object: this.props.object,
+      }),
+      div(
+        { className: "treeTableBox devtools-monospace" },
+        DomTree({
+          filter,
+          object,
+          openLink: url => DomProvider.openLink(url),
+        })
+      )
+    );
+  }
+}
+
+// Transform state into props
+// Note: use https://github.com/faassen/reselect for better performance.
+const mapStateToProps = state => {
+  return {
+    filter: state.filter,
+  };
+};
+
+// Exports from this module
+module.exports = connect(mapStateToProps)(MainFrame);
diff --git a/devtools/client/dom/content/components/MainToolbar.js b/devtools/client/dom/content/components/MainToolbar.js
new file mode 100644
index 0000000000..342ba97e47
--- /dev/null
+++ b/devtools/client/dom/content/components/MainToolbar.js
@@ -0,0 +1,76 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+// React
+const {
+  Component,
+  createFactory,
+} = require("devtools/client/shared/vendor/react");
+const dom = require("devtools/client/shared/vendor/react-dom-factories");
+const PropTypes = require("devtools/client/shared/vendor/react-prop-types");
+const SearchBox = createFactory(
+  require("devtools/client/shared/components/SearchBox")
+);
+
+const { l10n } = require("devtools/client/dom/content/utils");
+
+// Actions
+const {
+  fetchProperties,
+} = require("devtools/client/dom/content/actions/grips");
+const {
+  setVisibilityFilter,
+} = require("devtools/client/dom/content/actions/filter");
+
+/**
+ * This template is responsible for rendering a toolbar
+ * within the 'Headers' panel.
+ */
+class MainToolbar extends Component {
+  static get propTypes() {
+    return {
+      object: PropTypes.any.isRequired,
+      dispatch: PropTypes.func.isRequired,
+    };
+  }
+
+  constructor(props) {
+    super(props);
+    this.onRefresh = this.onRefresh.bind(this);
+    this.onSearch = this.onSearch.bind(this);
+  }
+
+  onRefresh() {
+    this.props.dispatch(fetchProperties(this.props.object));
+  }
+
+  onSearch(value) {
+    this.props.dispatch(setVisibilityFilter(value));
+  }
+
+  render() {
+    return dom.div(
+      { className: "devtools-toolbar devtools-input-toolbar" },
+      SearchBox({
+        key: "filter",
+        delay: 250,
+        onChange: this.onSearch,
+        placeholder: l10n.getStr("dom.filterDOMPanel"),
+        type: "filter",
+      }),
+      dom.span({ className: "devtools-separator" }),
+      dom.button({
+        key: "refresh",
+        className: "refresh devtools-button",
+        id: "dom-refresh-button",
+        title: l10n.getStr("dom.refresh"),
+        onClick: this.onRefresh,
+      })
+    );
+  }
+}
+
+// Exports from this module
+module.exports = MainToolbar;
diff --git a/devtools/client/dom/content/components/moz.build b/devtools/client/dom/content/components/moz.build
new file mode 100644
index 0000000000..5b669bac24
--- /dev/null
+++ b/devtools/client/dom/content/components/moz.build
@@ -0,0 +1,6 @@
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules("DomTree.js", "MainFrame.js", "MainToolbar.js")
diff --git a/devtools/client/dom/content/constants.js b/devtools/client/dom/content/constants.js
new file mode 100644
index 0000000000..c7bb8b325c
--- /dev/null
+++ b/devtools/client/dom/content/constants.js
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+exports.FETCH_PROPERTIES = "FETCH_PROPERTIES";
+exports.SET_VISIBILITY_FILTER = "SET_VISIBILITY_FILTER";
diff --git a/devtools/client/dom/content/dom-decorator.js b/devtools/client/dom/content/dom-decorator.js
new file mode 100644
index 0000000000..39c18330da
--- /dev/null
+++ b/devtools/client/dom/content/dom-decorator.js
@@ -0,0 +1,46 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const { Property } = require("devtools/client/dom/content/reducers/grips");
+
+// Implementation
+
+function DomDecorator() {}
+
+/**
+ * Decorator for DOM panel tree component. It's responsible for
+ * appending an icon to read only properties.
+ */
+DomDecorator.prototype = {
+  getRowClass: function(object) {
+    if (object instanceof Property) {
+      const value = object.value;
+      const names = [];
+
+      if (value.enumerable) {
+        names.push("enumerable");
+      }
+      if (value.writable) {
+        names.push("writable");
+      }
+      if (value.configurable) {
+        names.push("configurable");
+      }
+
+      return names;
+    }
+
+    return null;
+  },
+
+  /**
+   * Return custom React template for specified object. The template
+   * might depend on specified column.
+   */
+  getValueRep: function(value, colId) {},
+};
+
+// Exports from this module
+exports.DomDecorator = DomDecorator;
diff --git a/devtools/client/dom/content/dom-view.css b/devtools/client/dom/content/dom-view.css
new file mode 100644
index 0000000000..d2fd77e525
--- /dev/null
+++ b/devtools/client/dom/content/dom-view.css
@@ -0,0 +1,109 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/******************************************************************************/
+/* General */
+
+body {
+  padding: 0;
+  margin: 0;
+  overflow: hidden;
+  background-color: var(--theme-body-background);
+}
+
+.mainFrame {
+  display: flex;
+  flex-direction: column;
+  height: 100vh;
+}
+
+.mainFrame > .treeTableBox {
+  flex: 1 1 auto;
+  overflow: auto;
+}
+
+/******************************************************************************/
+/* TreeView Customization */
+
+.treeTable {
+  width: 100%;
+}
+
+/* Space for read only properties icon */
+.treeTable td.treeValueCell {
+  padding-inline-start: 16px;
+}
+
+.treeTable .treeLabel,
+.treeTable td.treeValueCell .objectBox {
+  direction: ltr; /* Don't change the direction of english labels */
+}
+
+/* Read only properties have a padlock icon */
+.treeTable tr:not(.writable) td.treeValueCell {
+  background: url("chrome://devtools/skin/images/lock.svg") no-repeat;
+  background-position: 1px 4px;
+  background-size: 12px 12px;
+  -moz-context-properties: fill;
+  fill: var(--theme-icon-dimmed-color);
+}
+
+.treeTable tr:not(.writable) td.treeValueCell:dir(rtl) {
+  background-position-x: right 1px;
+}
+
+.treeTable tr:not(.writable).selected td.treeValueCell {
+  fill: var(--theme-selection-color);
+}
+
+/* Non-enumerable properties are grayed out */
+.treeTable tr:not(.enumerable) td.treeValueCell {
+  opacity: 0.7;
+}
+
+.theme-light .treeTable > tbody > tr > td {
+  border-bottom: 1px solid var(--grey-20);
+}
+
+/* Label Types */
+.treeTable .userLabel,
+.treeTable .userClassLabel,
+.treeTable .userFunctionLabel {
+  font-weight: bold;
+}
+
+.treeTable .userLabel {
+  color: #000000;
+}
+
+.treeTable .userClassLabel {
+  color: #E90000;
+}
+
+.treeTable .userFunctionLabel {
+  color: #025E2A;
+}
+
+.treeTable .domLabel {
+  color: #000000;
+}
+
+.treeTable .domClassLabel {
+  color: #E90000;
+}
+
+.treeTable .domFunctionLabel {
+  color: #025E2A;
+}
+
+.treeTable .ordinalLabel {
+  color: SlateBlue;
+  font-weight: bold;
+}
+
+/******************************************************************************/
+/* Refresh button */
+#dom-refresh-button::before {
+  background-image: url("chrome://devtools/skin/images/reload.svg");
+}
diff --git a/devtools/client/dom/content/dom-view.js b/devtools/client/dom/content/dom-view.js
new file mode 100644
index 0000000000..69aa489279
--- /dev/null
+++ b/devtools/client/dom/content/dom-view.js
@@ -0,0 +1,65 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+// React & Redux
+const React = require("devtools/client/shared/vendor/react");
+const ReactDOM = require("devtools/client/shared/vendor/react-dom");
+const { Provider } = require("devtools/client/shared/vendor/react-redux");
+
+// DOM Panel
+const MainFrame = React.createFactory(
+  require("devtools/client/dom/content/components/MainFrame")
+);
+
+// Store
+const createStore = require("devtools/client/shared/redux/create-store");
+
+const { reducers } = require("devtools/client/dom/content/reducers/index");
+const store = createStore(reducers);
+
+/**
+ * This object represents view of the DOM panel and is responsible
+ * for rendering the content. It renders the top level ReactJS
+ * component: the MainFrame.
+ */
+function DomView(localStore) {
+  addEventListener("devtools/chrome/message", this.onMessage.bind(this), true);
+
+  // Make it local so, tests can access it.
+  this.store = localStore;
+}
+
+DomView.prototype = {
+  initialize: function(rootGrip) {
+    const content = document.querySelector("#content");
+    const mainFrame = MainFrame({
+      object: rootGrip,
+    });
+
+    // Render top level component
+    const provider = React.createElement(
+      Provider,
+      {
+        store: this.store,
+      },
+      mainFrame
+    );
+
+    this.mainFrame = ReactDOM.render(provider, content);
+  },
+
+  onMessage: function(event) {
+    const data = event.data;
+    const method = data.type;
+
+    if (typeof this[method] == "function") {
+      this[method](data.args);
+    }
+  },
+};
+
+// Construct DOM panel view object and expose it to tests.
+// Tests can access it through: |panel.panelWin.view|
+window.view = new DomView(store);
diff --git a/devtools/client/dom/content/grip-provider.js b/devtools/client/dom/content/grip-provider.js
new file mode 100644
index 0000000000..1988369a77
--- /dev/null
+++ b/devtools/client/dom/content/grip-provider.js
@@ -0,0 +1,100 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const {
+  fetchProperties,
+} = require("devtools/client/dom/content/actions/grips");
+const { Property } = require("devtools/client/dom/content/reducers/grips");
+
+// Implementation
+function GripProvider(grips, dispatch) {
+  this.grips = grips;
+  this.dispatch = dispatch;
+}
+
+/**
+ * This object provides data for the tree displayed in the tooltip
+ * content.
+ */
+GripProvider.prototype = {
+  /**
+   * Fetches properties from the backend. These properties might be
+   * displayed as child objects in e.g. a tree UI widget.
+   */
+  getChildren: function(object) {
+    let grip = object;
+    if (object instanceof Property) {
+      grip = this.getValue(object);
+    }
+
+    if (!grip || !grip.actorID) {
+      return [];
+    }
+
+    const props = this.grips.get(grip.actorID);
+    if (!props) {
+      // Fetch missing data from the backend. Returning a promise
+      // from data provider causes the tree to show a spinner.
+      return this.dispatch(fetchProperties(grip));
+    }
+
+    return props;
+  },
+
+  hasChildren: function(object) {
+    if (object instanceof Property) {
+      const value = this.getValue(object);
+      if (!value) {
+        return false;
+      }
+      const grip = value?.getGrip ? value.getGrip() : value;
+
+      let hasChildren = grip.ownPropertyLength > 0;
+
+      if (grip.preview) {
+        hasChildren = hasChildren || grip.preview.ownPropertiesLength > 0;
+      }
+
+      if (grip.preview) {
+        const preview = grip.preview;
+        const k = preview.kind;
+        const objectsWithProps = ["DOMNode", "ObjectWithURL"];
+        hasChildren = hasChildren || objectsWithProps.includes(k);
+        hasChildren = hasChildren || (k == "ArrayLike" && preview.length > 0);
+      }
+
+      return grip.type == "object" && hasChildren;
+    }
+
+    return null;
+  },
+
+  getValue: function(object) {
+    if (object instanceof Property) {
+      const value = object.value;
+      return typeof value.value != "undefined"
+        ? value.value
+        : value.getterValue;
+    }
+
+    return object;
+  },
+
+  getLabel: function(object) {
+    return object instanceof Property ? object.name : null;
+  },
+
+  getKey: function(object) {
+    return object instanceof Property ? object.key : null;
+  },
+
+  getType: function(object) {
+    const grip = object?.getGrip ? object.getGrip() : object;
+    return grip.class ? grip.class : "";
+  },
+};
+
+// Exports from this module
+exports.GripProvider = GripProvider;
diff --git a/devtools/client/dom/content/moz.build b/devtools/client/dom/content/moz.build
new file mode 100644
index 0000000000..04e0ac4efc
--- /dev/null
+++ b/devtools/client/dom/content/moz.build
@@ -0,0 +1,18 @@
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIRS += [
+    "actions",
+    "components",
+    "reducers",
+]
+
+DevToolsModules(
+    "constants.js",
+    "dom-decorator.js",
+    "dom-view.js",
+    "grip-provider.js",
+    "utils.js",
+)
diff --git a/devtools/client/dom/content/reducers/filter.js b/devtools/client/dom/content/reducers/filter.js
new file mode 100644
index 0000000000..428dca2e4c
--- /dev/null
+++ b/devtools/client/dom/content/reducers/filter.js
@@ -0,0 +1,27 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const constants = require("devtools/client/dom/content/constants");
+
+/**
+ * Initial state definition
+ */
+function getInitialState() {
+  return "";
+}
+
+/**
+ * Filter displayed object properties.
+ */
+function filter(state = getInitialState(), action) {
+  if (action.type == constants.SET_VISIBILITY_FILTER) {
+    return action.filter;
+  }
+
+  return state;
+}
+
+// Exports from this module
+exports.filter = filter;
diff --git a/devtools/client/dom/content/reducers/grips.js b/devtools/client/dom/content/reducers/grips.js
new file mode 100644
index 0000000000..acfb1146f2
--- /dev/null
+++ b/devtools/client/dom/content/reducers/grips.js
@@ -0,0 +1,123 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const constants = require("devtools/client/dom/content/constants");
+
+/**
+ * Initial state definition
+ */
+function getInitialState() {
+  return new Map();
+}
+
+/**
+ * Maintain a cache of received grip responses from the backend.
+ */
+function grips(state = getInitialState(), action) {
+  // This reducer supports only one action, fetching actor properties
+  // from the backend so, bail out if we are dealing with any other
+  // action.
+  if (action.type != constants.FETCH_PROPERTIES) {
+    return state;
+  }
+
+  switch (action.status) {
+    case "start":
+      return onRequestProperties(state, action);
+    case "end":
+      return onReceiveProperties(state, action);
+  }
+
+  return state;
+}
+
+/**
+ * Handle requestProperties action
+ */
+function onRequestProperties(state, action) {
+  return state;
+}
+
+/**
+ * Handle receiveProperties action
+ */
+function onReceiveProperties(cache, action) {
+  const response = action.response;
+  const from = response.from;
+  const className = action.grip?.getGrip
+    ? action.grip.getGrip().class
+    : action.grip.class;
+
+  // Properly deal with getters.
+  mergeProperties(response);
+
+  // Compute list of requested children.
+  const previewProps = response.preview ? response.preview.ownProperties : null;
+  const ownProps = response.ownProperties || previewProps || [];
+
+  const props = Object.keys(ownProps).map(key => {
+    // Array indexes as a special case. We convert any keys that are string
+    // representations of integers to integers.
+    if (className === "Array" && isInteger(key)) {
+      key = parseInt(key, 10);
+    }
+    return new Property(key, ownProps[key], key);
+  });
+
+  props.sort(sortName);
+
+  // Return new state/map.
+  const newCache = new Map(cache);
+  newCache.set(from, props);
+
+  return newCache;
+}
+
+// Helpers
+
+function mergeProperties(response) {
+  const { ownProperties } = response;
+
+  // 'safeGetterValues' is new and isn't necessary defined on old grips.
+  const safeGetterValues = response.safeGetterValues || {};
+
+  // Merge the safe getter values into one object such that we can use it
+  // in variablesView.
+  for (const name of Object.keys(safeGetterValues)) {
+    if (name in ownProperties) {
+      const { getterValue, getterPrototypeLevel } = safeGetterValues[name];
+      ownProperties[name].getterValue = getterValue;
+      ownProperties[name].getterPrototypeLevel = getterPrototypeLevel;
+    } else {
+      ownProperties[name] = safeGetterValues[name];
+    }
+  }
+}
+
+function sortName(a, b) {
+  // Display non-enumerable properties at the end.
+  if (!a.value.enumerable && b.value.enumerable) {
+    return 1;
+  }
+  if (a.value.enumerable && !b.value.enumerable) {
+    return -1;
+  }
+  return a.name > b.name ? 1 : -1;
+}
+
+function isInteger(n) {
+  // We use parseInt(n, 10) == n to disregard scientific notation e.g. "3e24"
+  return isFinite(n) && parseInt(n, 10) == n;
+}
+
+function Property(name, value, key) {
+  this.name = name;
+  this.value = value;
+  this.key = key;
+}
+
+// Exports from this module
+exports.grips = grips;
+exports.Property = Property;
diff --git a/devtools/client/dom/content/reducers/index.js b/devtools/client/dom/content/reducers/index.js
new file mode 100644
index 0000000000..a6d1fa47b8
--- /dev/null
+++ b/devtools/client/dom/content/reducers/index.js
@@ -0,0 +1,12 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const { grips } = require("devtools/client/dom/content/reducers/grips");
+const { filter } = require("devtools/client/dom/content/reducers/filter");
+
+exports.reducers = {
+  grips,
+  filter,
+};
diff --git a/devtools/client/dom/content/reducers/moz.build b/devtools/client/dom/content/reducers/moz.build
new file mode 100644
index 0000000000..8d98444e34
--- /dev/null
+++ b/devtools/client/dom/content/reducers/moz.build
@@ -0,0 +1,10 @@
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "filter.js",
+    "grips.js",
+    "index.js",
+)
diff --git a/devtools/client/dom/content/utils.js b/devtools/client/dom/content/utils.js
new file mode 100644
index 0000000000..c0632d0e97
--- /dev/null
+++ b/devtools/client/dom/content/utils.js
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+/**
+ * The default localization just returns the last part of the key
+ * (all after the last dot).
+ */
+const DefaultL10N = {
+  getStr: function(key) {
+    const index = key.lastIndexOf(".");
+    return key.substr(index + 1);
+  },
+};
+
+/**
+ * The 'l10n' object is set by main.js in case the DOM panel content
+ * runs within a scope with chrome privileges.
+ *
+ * Note that DOM panel content can also run within a scope with no chrome
+ * privileges, e.g. in an iframe with type 'content' or in a browser tab,
+ * which allows using our own tools for development.
+ */
+exports.l10n = window.l10n || DefaultL10N;
diff --git a/devtools/client/dom/index.html b/devtools/client/dom/index.html
new file mode 100644
index 0000000000..0e4fd84b76
--- /dev/null
+++ b/devtools/client/dom/index.html
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<!DOCTYPE html>
+<html dir="">
+<head>
+  <meta charset="utf-8"/>
+
+  <link href="chrome://devtools/content/dom/content/dom-view.css" rel="stylesheet" />
+  <link href="chrome://devtools-jsonview-styles/content/toolbar.css" rel="stylesheet" />
+  <link href="chrome://devtools/content/shared/components/tree/TreeView.css" rel="stylesheet" />
+
+  <script src="chrome://devtools/content/shared/theme-switching.js"></script>
+</head>
+<body class="theme-body" role="application">
+  <div id="content"></div>
+  <script src="./main.js"></script>
+</body>
+</html>
diff --git a/devtools/client/dom/main.js b/devtools/client/dom/main.js
new file mode 100644
index 0000000000..efcb1a2b8e
--- /dev/null
+++ b/devtools/client/dom/main.js
@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const { XPCOMUtils } = ChromeUtils.import(
+  "resource://gre/modules/XPCOMUtils.jsm"
+);
+const { BrowserLoader } = ChromeUtils.import(
+  "resource://devtools/client/shared/browser-loader.js"
+);
+
+// Module Loader
+const require = BrowserLoader({
+  baseURI: "resource://devtools/client/dom/",
+  window,
+}).require;
+
+XPCOMUtils.defineConstant(this, "require", require);
+
+// Localization
+const { LocalizationHelper } = require("devtools/shared/l10n");
+this.l10n = new LocalizationHelper("devtools/client/locales/dom.properties");
+
+// Load DOM panel content
+require("devtools/client/dom/content/dom-view.js");
diff --git a/devtools/client/dom/moz.build b/devtools/client/dom/moz.build
new file mode 100644
index 0000000000..6e4380260a
--- /dev/null
+++ b/devtools/client/dom/moz.build
@@ -0,0 +1,17 @@
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+BROWSER_CHROME_MANIFESTS += ["test/browser.ini"]
+
+DIRS += [
+    "content",
+]
+
+DevToolsModules(
+    "panel.js",
+)
+
+with Files("**"):
+    BUG_COMPONENT = ("DevTools", "DOM")
diff --git a/devtools/client/dom/panel.js b/devtools/client/dom/panel.js
new file mode 100644
index 0000000000..a6110748a5
--- /dev/null
+++ b/devtools/client/dom/panel.js
@@ -0,0 +1,258 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const { Cu } = require("chrome");
+
+const EventEmitter = require("devtools/shared/event-emitter");
+loader.lazyRequireGetter(
+  this,
+  "openContentLink",
+  "devtools/client/shared/link",
+  true
+);
+
+/**
+ * This object represents DOM panel. It's responsibility is to
+ * render Document Object Model of the current debugger target.
+ */
+function DomPanel(iframeWindow, toolbox) {
+  this.panelWin = iframeWindow;
+  this._toolbox = toolbox;
+
+  this.onTabNavigated = this.onTabNavigated.bind(this);
+  this.onTargetAvailable = this.onTargetAvailable.bind(this);
+  this.onContentMessage = this.onContentMessage.bind(this);
+  this.onPanelVisibilityChange = this.onPanelVisibilityChange.bind(this);
+
+  this.pendingRequests = new Map();
+
+  EventEmitter.decorate(this);
+}
+
+DomPanel.prototype = {
+  /**
+   * Open is effectively an asynchronous constructor.
+   *
+   * @return object
+   *         A promise that is resolved when the DOM panel completes opening.
+   */
+  async open() {
+    // Wait for the retrieval of root object properties before resolving open
+    const onGetProperties = new Promise(resolve => {
+      this._resolveOpen = resolve;
+    });
+
+    this.initialize();
+
+    await onGetProperties;
+
+    this.isReady = true;
+    this.emit("ready");
+
+    return this;
+  },
+
+  // Initialization
+
+  initialize: function() {
+    this.panelWin.addEventListener(
+      "devtools/content/message",
+      this.onContentMessage,
+      true
+    );
+
+    this._toolbox.on("select", this.onPanelVisibilityChange);
+
+    this._toolbox.targetList.watchTargets(
+      [this._toolbox.targetList.TYPES.FRAME],
+      this.onTargetAvailable
+    );
+
+    // Export provider object with useful API for DOM panel.
+    const provider = {
+      getToolbox: this.getToolbox.bind(this),
+      getPrototypeAndProperties: this.getPrototypeAndProperties.bind(this),
+      openLink: this.openLink.bind(this),
+      // Resolve DomPanel.open once the object properties are fetched
+      onPropertiesFetched: () => {
+        if (this._resolveOpen) {
+          this._resolveOpen();
+          this._resolveOpen = null;
+        }
+      },
+    };
+
+    exportIntoContentScope(this.panelWin, provider, "DomProvider");
+  },
+
+  destroy() {
+    if (this._destroyed) {
+      return;
+    }
+    this._destroyed = true;
+
+    this.currentTarget.off("navigate", this.onTabNavigated);
+    this._toolbox.off("select", this.onPanelVisibilityChange);
+
+    this.emit("destroyed");
+  },
+
+  // Events
+
+  refresh: function() {
+    // Do not refresh if the panel isn't visible.
+    if (!this.isPanelVisible()) {
+      return;
+    }
+
+    // Do not refresh if it isn't necessary.
+    if (!this.shouldRefresh) {
+      return;
+    }
+
+    // Alright reset the flag we are about to refresh the panel.
+    this.shouldRefresh = false;
+
+    this.getRootGrip().then(rootGrip => {
+      this.postContentMessage("initialize", rootGrip);
+    });
+  },
+
+  /**
+   * Make sure the panel is refreshed when navigation occurs.
+   * The panel is refreshed immediately if it's currently selected or lazily when the user
+   * actually selects it.
+   */
+  onTabNavigated: function() {
+    this.shouldRefresh = true;
+    this.refresh();
+  },
+
+  onTargetAvailable: function({ targetFront }) {
+    // Only care about top-level targets.
+    if (!targetFront.isTopLevel) {
+      return;
+    }
+
+    this.shouldRefresh = true;
+    this.refresh();
+
+    // Whenever a new target is available, listen to navigate events on it so we can
+    // refresh the panel when we navigate within the same process.
+    this.currentTarget.on("navigate", this.onTabNavigated);
+  },
+
+  /**
+   * Make sure the panel is refreshed (if needed) when it's selected.
+   */
+  onPanelVisibilityChange: function() {
+    this.refresh();
+  },
+
+  // Helpers
+
+  /**
+   * Return true if the DOM panel is currently selected.
+   */
+  isPanelVisible: function() {
+    return this._toolbox.currentToolId === "dom";
+  },
+
+  getPrototypeAndProperties: async function(objectFront) {
+    if (!objectFront.actorID) {
+      console.error("No actor!", objectFront);
+      throw new Error("Failed to get object front.");
+    }
+
+    // Bail out if target doesn't exist (toolbox maybe closed already).
+    if (!this.currentTarget) {
+      return null;
+    }
+
+    // Check for a previously stored request for grip.
+    let request = this.pendingRequests.get(objectFront.actorID);
+
+    // If no request is in progress create a new one.
+    if (!request) {
+      request = objectFront.getPrototypeAndProperties();
+      this.pendingRequests.set(objectFront.actorID, request);
+    }
+
+    const response = await request;
+    this.pendingRequests.delete(objectFront.actorID);
+
+    // Fire an event about not having any pending requests.
+    if (!this.pendingRequests.size) {
+      this.emit("no-pending-requests");
+    }
+
+    return response;
+  },
+
+  openLink: function(url) {
+    openContentLink(url);
+  },
+
+  getRootGrip: async function() {
+    // Attach Console. It might involve RDP communication, so wait
+    // asynchronously for the result
+    const consoleFront = await this.currentTarget.getFront("console");
+    const { result } = await consoleFront.evaluateJSAsync("window");
+    return result;
+  },
+
+  postContentMessage: function(type, args) {
+    const data = {
+      type: type,
+      args: args,
+    };
+
+    const event = new this.panelWin.MessageEvent("devtools/chrome/message", {
+      bubbles: true,
+      cancelable: true,
+      data: data,
+    });
+
+    this.panelWin.dispatchEvent(event);
+  },
+
+  onContentMessage: function(event) {
+    const data = event.data;
+    const method = data.type;
+    if (typeof this[method] == "function") {
+      this[method](data.args);
+    }
+  },
+
+  getToolbox: function() {
+    return this._toolbox;
+  },
+
+  get currentTarget() {
+    return this._toolbox.target;
+  },
+};
+
+// Helpers
+
+function exportIntoContentScope(win, obj, defineAs) {
+  const clone = Cu.createObjectIn(win, {
+    defineAs: defineAs,
+  });
+
+  const props = Object.getOwnPropertyNames(obj);
+  for (let i = 0; i < props.length; i++) {
+    const propName = props[i];
+    const propValue = obj[propName];
+    if (typeof propValue == "function") {
+      Cu.exportFunction(propValue, clone, {
+        defineAs: propName,
+      });
+    }
+  }
+}
+
+// Exports from this module
+exports.DomPanel = DomPanel;
diff --git a/devtools/client/dom/test/.eslintrc.js b/devtools/client/dom/test/.eslintrc.js
new file mode 100644
index 0000000000..3d0bd99e1b
--- /dev/null
+++ b/devtools/client/dom/test/.eslintrc.js
@@ -0,0 +1,6 @@
+"use strict";
+
+module.exports = {
+  // Extend from the shared list of defined globals for mochitests.
+  extends: "../../../.eslintrc.mochitests.js",
+};
diff --git a/devtools/client/dom/test/browser.ini b/devtools/client/dom/test/browser.ini
new file mode 100644
index 0000000000..067664afb3
--- /dev/null
+++ b/devtools/client/dom/test/browser.ini
@@ -0,0 +1,17 @@
+[DEFAULT]
+tags = devtools
+subsuite = devtools
+support-files =
+  head.js
+  page_array.html
+  page_basic.html
+  page_dom_nodes.html
+  !/devtools/client/shared/test/shared-head.js
+  !/devtools/client/shared/test/telemetry-test-helpers.js
+
+[browser_dom_array.js]
+[browser_dom_basic.js]
+[browser_dom_fission_target_switching.js]
+[browser_dom_nodes_highlight.js]
+[browser_dom_nodes_select.js]
+[browser_dom_refresh.js]
diff --git a/devtools/client/dom/test/browser_dom_array.js b/devtools/client/dom/test/browser_dom_array.js
new file mode 100644
index 0000000000..44fba5e11e
--- /dev/null
+++ b/devtools/client/dom/test/browser_dom_array.js
@@ -0,0 +1,66 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_PAGE_URL = URL_ROOT + "page_array.html";
+const TEST_ARRAY = [
+  "a",
+  "b",
+  "c",
+  "d",
+  "e",
+  "f",
+  "g",
+  "h",
+  "i",
+  "j",
+  "k",
+  "l",
+  "m",
+  "n",
+  "o",
+  "p",
+  "q",
+  "r",
+  "s",
+  "t",
+  "u",
+  "v",
+  "w",
+  "x",
+  "y",
+  "z",
+];
+
+/**
+ * Basic test that checks content of the DOM panel.
+ */
+add_task(async function() {
+  info("Test DOM Panel Array Expansion started");
+
+  const { panel } = await addTestTab(TEST_PAGE_URL);
+
+  // Expand specified row and wait till children are displayed.
+  await expandRow(panel, "_a");
+
+  // Verify that children is displayed now.
+  const childRows = getAllRowsForLabel(panel, "_a");
+
+  const item = childRows.pop();
+  is(item.name, "length", "length property is correct");
+  is(item.value, 26, "length property value is 26");
+
+  let i = 0;
+  for (const name in childRows) {
+    const row = childRows[name];
+
+    is(
+      parseInt(name, 10),
+      i++,
+      `index ${name} is correct and sorted into the correct position`
+    );
+    ok(typeof row.name === "number", "array index is displayed as a number");
+    is(TEST_ARRAY[name], row.value, `value for array[${name}] is ${row.value}`);
+  }
+});
diff --git a/devtools/client/dom/test/browser_dom_basic.js b/devtools/client/dom/test/browser_dom_basic.js
new file mode 100644
index 0000000000..532a6da3fd
--- /dev/null
+++ b/devtools/client/dom/test/browser_dom_basic.js
@@ -0,0 +1,22 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_PAGE_URL = URL_ROOT + "page_basic.html";
+
+/**
+ * Basic test that checks content of the DOM panel.
+ */
+add_task(async function() {
+  info("Test DOM panel basic started");
+
+  const { panel } = await addTestTab(TEST_PAGE_URL);
+
+  // Expand specified row and wait till children are displayed.
+  await expandRow(panel, "_a");
+
+  // Verify that child is displayed now.
+  const childRow = getRowByLabel(panel, "_data");
+  ok(childRow, "Child row must exist");
+});
diff --git a/devtools/client/dom/test/browser_dom_fission_target_switching.js b/devtools/client/dom/test/browser_dom_fission_target_switching.js
new file mode 100644
index 0000000000..af9ca13f67
--- /dev/null
+++ b/devtools/client/dom/test/browser_dom_fission_target_switching.js
@@ -0,0 +1,40 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Test top-level target switching in the DOM panel.
+
+const PARENT_PROCESS_URI = "about:robots";
+const CONTENT_PROCESS_URI = URL_ROOT + "page_basic.html";
+
+add_task(async function() {
+  // We use about:robots as the starting page because it will run in the parent process.
+  // Navigating from that page to a regular content page will always trigger a target
+  // switch, with or without fission.
+
+  info("Open a page that runs in the parent process");
+  const { panel } = await addTestTab(PARENT_PROCESS_URI);
+
+  const _aProperty = getRowByLabel(panel, "_a");
+  let buttonProperty = getRowByLabel(panel, "button");
+
+  ok(!_aProperty, "There is no _a property on the about:robots page");
+  ok(buttonProperty, "There is, however, a button property on this page");
+
+  info("Navigate to a page that runs in the content process");
+  // Wait for the DOM panel to refresh.
+  const onPropertiesFetched = waitForDispatch(panel, "FETCH_PROPERTIES");
+  // Also wait for the toolbox to switch to the new target, to avoid hanging requests when
+  // the test ends.
+  await navigateTo(CONTENT_PROCESS_URI);
+  await onPropertiesFetched;
+
+  await waitFor(() => getRowByLabel(panel, "_a"));
+  ok(true, "This time, the _a property exists on this content process page");
+
+  buttonProperty = getRowByLabel(panel, "button");
+  ok(
+    !buttonProperty,
+    "There is, however, no more button property on this page"
+  );
+});
diff --git a/devtools/client/dom/test/browser_dom_nodes_highlight.js b/devtools/client/dom/test/browser_dom_nodes_highlight.js
new file mode 100644
index 0000000000..7f880a3a9b
--- /dev/null
+++ b/devtools/client/dom/test/browser_dom_nodes_highlight.js
@@ -0,0 +1,73 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_PAGE_URL = URL_ROOT + "page_dom_nodes.html";
+
+/**
+ * Checks that hovering nodes highlights them in the content page
+ */
+add_task(async function() {
+  info("Test DOM panel node highlight started");
+
+  const { panel } = await addTestTab(TEST_PAGE_URL);
+  const toolbox = gDevTools.getToolbox(panel.currentTarget);
+  const highlighter = toolbox.getHighlighter();
+
+  const tests = [
+    {
+      expected: "h1",
+      getNode: async () => {
+        return getRowByIndex(panel, 2).querySelector(".objectBox-node");
+      },
+    },
+    {
+      expected: "h2",
+      getNode: async () => {
+        info("Expand specified row and wait till children are displayed");
+        await expandRow(panel, "_b");
+        return getRowByIndex(panel, 3).querySelector(".objectBox-node");
+      },
+    },
+  ];
+
+  for (const test of tests) {
+    info(`Get the NodeFront for ${test.expected}`);
+    const node = await test.getNode();
+
+    info("Highlight the node by moving the cursor on it");
+    const onHighlighterShown = highlighter.waitForHighlighterShown();
+    EventUtils.synthesizeMouseAtCenter(
+      node,
+      {
+        type: "mouseover",
+      },
+      node.ownerDocument.defaultView
+    );
+    const { nodeFront } = await onHighlighterShown;
+    is(
+      nodeFront.displayName,
+      test.expected,
+      "The correct node was highlighted"
+    );
+
+    info("Unhighlight the node by moving the cursor away from it");
+    const onHighlighterHidden = highlighter.waitForHighlighterHidden();
+    const btn = toolbox.doc.querySelector("#toolbox-meatball-menu-button");
+    EventUtils.synthesizeMouseAtCenter(
+      btn,
+      {
+        type: "mouseover",
+      },
+      btn.ownerDocument.defaultView
+    );
+
+    const { nodeFront: unhighlightedNode } = await onHighlighterHidden;
+    is(
+      unhighlightedNode.displayName,
+      test.expected,
+      "The node was unhighlighted"
+    );
+  }
+});
diff --git a/devtools/client/dom/test/browser_dom_nodes_select.js b/devtools/client/dom/test/browser_dom_nodes_select.js
new file mode 100644
index 0000000000..8b7724294d
--- /dev/null
+++ b/devtools/client/dom/test/browser_dom_nodes_select.js
@@ -0,0 +1,43 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_PAGE_URL = URL_ROOT + "page_dom_nodes.html";
+
+/**
+ * Checks whether hovering nodes highlight them in the content page
+ */
+add_task(async function() {
+  info("Test DOM panel node highlight started");
+
+  const { panel } = await addTestTab(TEST_PAGE_URL);
+  const toolbox = gDevTools.getToolbox(panel.currentTarget);
+  const node = getRowByIndex(panel, 2);
+
+  // Loading the inspector panel at first, to make it possible to listen for
+  // new node selections
+
+  await toolbox.loadTool("inspector");
+  const inspector = toolbox.getPanel("inspector");
+
+  const openInInspectorIcon = node.querySelector(".open-inspector");
+  ok(node !== null, "Node was logged as expected");
+
+  info(
+    "Clicking on the inspector icon and waiting for the " +
+      "inspector to be selected"
+  );
+  const onInspectorSelected = toolbox.once("inspector-selected");
+  const onInspectorUpdated = inspector.once("inspector-updated");
+  const onNewNode = toolbox.selection.once("new-node-front");
+
+  openInInspectorIcon.click();
+
+  await onInspectorSelected;
+  await onInspectorUpdated;
+  const nodeFront = await onNewNode;
+
+  ok(true, "Inspector selected and new node got selected");
+  is(nodeFront.displayName, "h1", "The expected node was selected");
+});
diff --git a/devtools/client/dom/test/browser_dom_refresh.js b/devtools/client/dom/test/browser_dom_refresh.js
new file mode 100644
index 0000000000..905f15e873
--- /dev/null
+++ b/devtools/client/dom/test/browser_dom_refresh.js
@@ -0,0 +1,23 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_PAGE_URL = URL_ROOT + "page_basic.html";
+
+/**
+ * Basic test that checks the Refresh action in DOM panel.
+ */
+add_task(async function() {
+  info("Test DOM panel basic started");
+
+  const { panel } = await addTestTab(TEST_PAGE_URL);
+
+  // Create a new variable in the page scope and refresh the panel.
+  await evaluateJSAsync(panel, "var _b = 10");
+  await refreshPanel(panel);
+
+  // Verify that the variable is displayed now.
+  const row = getRowByLabel(panel, "_b");
+  ok(row, "New variable must be displayed");
+});
diff --git a/devtools/client/dom/test/head.js b/devtools/client/dom/test/head.js
new file mode 100644
index 0000000000..d812e96187
--- /dev/null
+++ b/devtools/client/dom/test/head.js
@@ -0,0 +1,243 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+/* eslint no-unused-vars: [2, {"vars": "local", "args": "none"}] */
+/* import-globals-from ../../shared/test/shared-head.js */
+
+"use strict";
+
+// shared-head.js handles imports, constants, and utility functions
+Services.scriptloader.loadSubScript(
+  "chrome://mochitests/content/browser/devtools/client/shared/test/shared-head.js",
+  this
+);
+
+// DOM panel actions.
+const constants = require("devtools/client/dom/content/constants");
+
+// Uncomment this pref to dump all devtools emitted events to the console.
+// Services.prefs.setBoolPref("devtools.dom.enabled", true);
+
+// Enable the DOM panel
+Services.prefs.setBoolPref("devtools.dom.enabled", true);
+
+registerCleanupFunction(() => {
+  info("finish() was called, cleaning up...");
+  Services.prefs.clearUserPref("devtools.dump.emit");
+  Services.prefs.clearUserPref("devtools.dom.enabled");
+});
+
+/**
+ * Add a new test tab in the browser and load the given url.
+ * @param {String} url
+ *        The url to be loaded in the new tab
+ * @return a promise that resolves to the tab object when
+ *        the url is loaded
+ */
+async function addTestTab(url) {
+  info("Adding a new test tab with URL: '" + url + "'");
+
+  const tab = await addTab(url);
+
+  // Select the DOM panel and wait till it's initialized.
+  const panel = await initDOMPanel(tab);
+
+  // FETCH_PROPERTIES should be fired during the call to initDOMPanel
+  // But note that this behavior changed during a change in webconsole
+  // initialization. So this might be racy.
+  const doc = panel.panelWin.document;
+  const nodes = [...doc.querySelectorAll(".treeLabel")];
+  ok(nodes.length > 0, "The DOM panel is already populated");
+
+  return {
+    tab,
+    browser: tab.linkedBrowser,
+    panel,
+  };
+}
+
+/**
+ * Open the DOM panel for the given tab.
+ *
+ * @param {Element} tab
+ *        Optional tab element for which you want open the DOM panel.
+ *        The default tab is taken from the global variable |tab|.
+ * @return a promise that is resolved once the web console is open.
+ */
+async function initDOMPanel(tab) {
+  const target = await TargetFactory.forTab(tab || gBrowser.selectedTab);
+  const toolbox = await gDevTools.showToolbox(target, "dom");
+  const panel = toolbox.getCurrentPanel();
+  return panel;
+}
+
+/**
+ * Synthesize asynchronous click event (with clean stack trace).
+ */
+function synthesizeMouseClickSoon(panel, element) {
+  return new Promise(resolve => {
+    executeSoon(() => {
+      EventUtils.synthesizeMouse(element, 2, 2, {}, panel.panelWin);
+      resolve();
+    });
+  });
+}
+
+/**
+ * Returns tree row with specified label.
+ */
+function getRowByLabel(panel, text) {
+  const doc = panel.panelWin.document;
+  const labels = [...doc.querySelectorAll(".treeLabel")];
+  const label = labels.find(node => node.textContent == text);
+  return label ? label.closest(".treeRow") : null;
+}
+
+/**
+ * Returns tree row with specified index.
+ */
+function getRowByIndex(panel, id) {
+  const doc = panel.panelWin.document;
+  const labels = [...doc.querySelectorAll(".treeLabel")];
+  const label = labels.find((node, i) => i == id);
+  return label ? label.closest(".treeRow") : null;
+}
+
+/**
+ * Returns the children (tree row text) of the specified object name as an
+ * array.
+ */
+function getAllRowsForLabel(panel, text) {
+  let rootObjectLevel;
+  let node;
+  const result = [];
+  const doc = panel.panelWin.document;
+  const nodes = [...doc.querySelectorAll(".treeLabel")];
+
+  // Find the label (object name) for which we want the children. We remove
+  // nodes from the start of the array until we reach the property. The children
+  // are then at the start of the array.
+  while (true) {
+    node = nodes.shift();
+
+    if (!node || node.textContent === text) {
+      rootObjectLevel = node.getAttribute("data-level");
+      break;
+    }
+  }
+
+  // Return an empty array if the node is not found.
+  if (!node) {
+    return result;
+  }
+
+  // Now get the children.
+  for (node of nodes) {
+    const level = node.getAttribute("data-level");
+
+    if (level > rootObjectLevel) {
+      result.push({
+        name: normalizeTreeValue(node.textContent),
+        value: normalizeTreeValue(
+          node.parentNode.nextElementSibling.textContent
+        ),
+      });
+    } else {
+      break;
+    }
+  }
+
+  return result;
+}
+
+/**
+ * Strings in the tree are in the form ""a"" and numbers in the form "1". We
+ * normalize these values by converting ""a"" to "a" and "1" to 1.
+ *
+ * @param  {String} value
+ *         The value to normalize.
+ * @return {String|Number}
+ *         The normalized value.
+ */
+function normalizeTreeValue(value) {
+  if (value === `""`) {
+    return "";
+  }
+  if (value.startsWith(`"`) && value.endsWith(`"`)) {
+    return value.substr(1, value.length - 2);
+  }
+  if (isFinite(value) && parseInt(value, 10) == value) {
+    return parseInt(value, 10);
+  }
+
+  return value;
+}
+
+/**
+ * Expands elements with given label and waits till
+ * children are received from the backend.
+ */
+function expandRow(panel, labelText) {
+  const row = getRowByLabel(panel, labelText);
+  return synthesizeMouseClickSoon(panel, row).then(() => {
+    // Wait till children (properties) are fetched
+    // from the backend.
+    return waitForDispatch(panel, "FETCH_PROPERTIES");
+  });
+}
+
+async function evaluateJSAsync(panel, expression) {
+  const consoleFront = await panel.currentTarget.getFront("console");
+  return consoleFront.evaluateJSAsync(expression);
+}
+
+function refreshPanel(panel) {
+  const doc = panel.panelWin.document;
+  const button = doc.querySelector("#dom-refresh-button");
+  return synthesizeMouseClickSoon(panel, button).then(() => {
+    // Wait till children (properties) are fetched
+    // from the backend.
+    return waitForDispatch(panel, "FETCH_PROPERTIES");
+  });
+}
+
+// Redux related API, use from shared location
+// as soon as bug 1261076 is fixed.
+
+// Wait until an action of `type` is dispatched. If it's part of an
+// async operation, wait until the `status` field is "done" or "error"
+function _afterDispatchDone(store, type) {
+  return new Promise(resolve => {
+    store.dispatch({
+      // Normally we would use `services.WAIT_UNTIL`, but use the
+      // internal name here so tests aren't forced to always pass it
+      // in
+      type: "@@service/waitUntil",
+      predicate: action => {
+        if (action.type === type) {
+          return action.status
+            ? action.status === "end" || action.status === "error"
+            : true;
+        }
+        return false;
+      },
+      run: (dispatch, getState, action) => {
+        resolve(action);
+      },
+    });
+  });
+}
+
+function waitForDispatch(panel, type, eventRepeat = 1) {
+  const store = panel.panelWin.view.mainFrame.store;
+  const actionType = constants[type];
+  let count = 0;
+
+  return (async function() {
+    info("Waiting for " + type + " to dispatch " + eventRepeat + " time(s)");
+    while (count < eventRepeat) {
+      await _afterDispatchDone(store, actionType);
+      count++;
+      info(type + " dispatched " + count + " time(s)");
+    }
+  })();
+}
diff --git a/devtools/client/dom/test/page_array.html b/devtools/client/dom/test/page_array.html
new file mode 100644
index 0000000000..848d6c4ce5
--- /dev/null
+++ b/devtools/client/dom/test/page_array.html
@@ -0,0 +1,19 @@
+<!-- Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/ -->
+<!doctype html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>DOM Panel Array Expansion Test Page</title>
+  </head>
+  <body>
+  <h2>DOM Panel Array Expansion Test Page</h2>
+  <script type="text/javascript">
+    "use strict";
+    window._a = [
+      "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m",
+      "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z",
+    ];
+  </script>
+  </body>
+</html>
diff --git a/devtools/client/dom/test/page_basic.html b/devtools/client/dom/test/page_basic.html
new file mode 100644
index 0000000000..170b3112a6
--- /dev/null
+++ b/devtools/client/dom/test/page_basic.html
@@ -0,0 +1,15 @@
+<!-- Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/ -->
+<!doctype html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>DOM test page</title>
+  </head>
+  <body>
+  <script type="text/javascript">
+    "use strict";
+    window._a = {_data: "test"};
+  </script>
+  </body>
+</html>
diff --git a/devtools/client/dom/test/page_dom_nodes.html b/devtools/client/dom/test/page_dom_nodes.html
new file mode 100644
index 0000000000..33d0655f9d
--- /dev/null
+++ b/devtools/client/dom/test/page_dom_nodes.html
@@ -0,0 +1,18 @@
+<!-- Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/ -->
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>DOM test hovering nodes page</title>
+  </head>
+  <body>
+    <h1 id="a">Node highlight test</h1>
+    <h2 id="b">Node highlight test inside object</h2>
+    <script>
+      "use strict";
+      window._a = document.getElementById("a");
+      window._b = {_data: document.getElementById("b")};
+    </script>
+  </body>
+</html>