--- a/devtools/client/inspector/animation/animation.js
+++ b/devtools/client/inspector/animation/animation.js
@@ -283,20 +283,20 @@ class AnimationInspector {
   }
 
   onElementPickerStopped() {
     this.inspector.store.dispatch(updateElementPickerEnabled(false));
   }
 
   onSidebarSelect() {
     this.update();
-    this.onSidebarResized(null, this.inspector.getSidebarSize());
+    this.onSidebarResized(this.inspector.getSidebarSize());
   }
 
-  onSidebarResized(type, size) {
+  onSidebarResized(size) {
     if (!this.isPanelVisible()) {
       return;
     }
 
     this.inspector.store.dispatch(updateSidebarSize(size));
   }
 
   removeAnimationsCurrentTimeListener(listener) {

--- a/devtools/client/inspector/computed/computed.js
+++ b/devtools/client/inspector/computed/computed.js
@@ -1412,17 +1412,17 @@ function ComputedViewTool(inspector, win
     this.inspector.pageStyle);
 
   this.onSelected = this.onSelected.bind(this);
   this.refresh = this.refresh.bind(this);
   this.onPanelSelected = this.onPanelSelected.bind(this);
   this.onMutations = this.onMutations.bind(this);
   this.onResized = this.onResized.bind(this);
 
-  this.inspector.selection.on("detached-front", this.onSelected);
+  this.inspector.selection.on("detached-front", this.onDetachedFront);
   this.inspector.selection.on("new-node-front", this.onSelected);
   this.inspector.selection.on("pseudoclass", this.refresh);
   this.inspector.sidebar.on("computedview-selected", this.onPanelSelected);
   this.inspector.pageStyle.on("stylesheet-updated", this.refresh);
   this.inspector.walker.on("mutations", this.onMutations);
   this.inspector.walker.on("resize", this.onResized);
 
   this.computedView.selectElement(null);
@@ -1433,17 +1433,21 @@ function ComputedViewTool(inspector, win
 ComputedViewTool.prototype = {
   isSidebarActive: function() {
     if (!this.computedView) {
       return false;
     }
     return this.inspector.sidebar.getCurrentTabID() == "computedview";
   },
 
-  onSelected: function(event) {
+  onDetachedFront: function() {
+    this.onSelected(false);
+  },
+
+  onSelected: function(selectElement = true) {
     // Ignore the event if the view has been destroyed, or if it's inactive.
     // But only if the current selection isn't null. If it's been set to null,
     // let the update go through as this is needed to empty the view on
     // navigation.
     if (!this.computedView) {
       return;
     }
 
@@ -1456,17 +1460,17 @@ ComputedViewTool.prototype = {
     this.computedView.setPageStyle(this.inspector.pageStyle);
 
     if (!this.inspector.selection.isConnected() ||
         !this.inspector.selection.isElementNode()) {
       this.computedView.selectElement(null);
       return;
     }
 
-    if (!event || event == "new-node-front") {
+    if (selectElement) {
       let done = this.inspector.updating("computed-view");
       this.computedView.selectElement(this.inspector.selection.nodeFront).then(() => {
         done();
       });
     }
   },
 
   refresh: function() {
@@ -1506,17 +1510,17 @@ ComputedViewTool.prototype = {
   },
 
   destroy: function() {
     this.inspector.walker.off("mutations", this.onMutations);
     this.inspector.walker.off("resize", this.onResized);
     this.inspector.sidebar.off("computedview-selected", this.refresh);
     this.inspector.selection.off("pseudoclass", this.refresh);
     this.inspector.selection.off("new-node-front", this.onSelected);
-    this.inspector.selection.off("detached-front", this.onSelected);
+    this.inspector.selection.off("detached-front", this.onDetachedFront);
     this.inspector.sidebar.off("computedview-selected", this.onPanelSelected);
     if (this.inspector.pageStyle) {
       this.inspector.pageStyle.off("stylesheet-updated", this.refresh);
     }
 
     this.computedView.destroy();
 
     this.computedView = this.document = this.inspector = null;

--- a/devtools/client/inspector/fonts/fonts.js
+++ b/devtools/client/inspector/fonts/fonts.js
@@ -148,17 +148,17 @@ class FontInspector {
   onPreviewFonts(value) {
     this.store.dispatch(updatePreviewText(value));
     this.update();
   }
 
   /**
    * Handler for the "theme-switched" event.
    */
-  onThemeChanged(event, frame) {
+  onThemeChanged(frame) {
     if (frame === this.document.defaultView) {
       this.update();
     }
   }
 
   async update() {
     // Stop refreshing if the inspector or store is already destroyed.
     if (!this.inspector || !this.store) {

--- a/devtools/client/inspector/inspector.js
+++ b/devtools/client/inspector/inspector.js
@@ -1153,17 +1153,17 @@ Inspector.prototype = {
            !selection.isAnonymousNode() &&
            !invalidTagNames.includes(
             selection.nodeFront.nodeName.toLowerCase());
   },
 
   /**
    * When a new node is selected.
    */
-  onNewSelection: function(event, value, reason) {
+  onNewSelection: function(value, reason) {
     if (reason === "selection-destroy") {
       return;
     }
 
     // Wait for all the known tools to finish updating and then let the
     // client know.
     let selection = this.selection.nodeFront;
 
@@ -1248,17 +1248,17 @@ Inspector.prototype = {
     this._updateProgress = null;
   },
 
   /**
    * When a node is deleted, select its parent node or the defaultNode if no
    * parent is found (may happen when deleting an iframe inside which the
    * node was selected).
    */
-  onDetached: function(event, parentNode) {
+  onDetached: function(parentNode) {
     this.breadcrumbs.cutAfter(this.breadcrumbs.indexOf(parentNode));
     this.selection.setNodeFront(parentNode ? parentNode : this._defaultNode, "detached");
   },
 
   /**
    * Destroy the inspector.
    */
   destroy: function() {

--- a/devtools/client/inspector/markup/markup.js
+++ b/devtools/client/inspector/markup/markup.js
@@ -176,17 +176,17 @@ MarkupView.prototype = {
     this.imagePreviewTooltip.startTogglingOnHover(this._elt,
       this._isImagePreviewTarget);
   },
 
   _disableImagePreviewTooltip: function() {
     this.imagePreviewTooltip.stopTogglingOnHover();
   },
 
-  _onToolboxPickerHover: function(event, nodeFront) {
+  _onToolboxPickerHover: function(nodeFront) {
     this.showNode(nodeFront).then(() => {
       this._showContainerAsHovered(nodeFront);
     }, console.error);
   },
 
   /**
    * If the element picker gets canceled, make sure and re-center the view on the
    * current selected element.

--- a/devtools/client/inspector/rules/rules.js
+++ b/devtools/client/inspector/rules/rules.js
@@ -1630,17 +1630,17 @@ function RuleViewTool(inspector, window)
   this.refresh = this.refresh.bind(this);
   this.onMutations = this.onMutations.bind(this);
   this.onPanelSelected = this.onPanelSelected.bind(this);
   this.onResized = this.onResized.bind(this);
   this.onSelected = this.onSelected.bind(this);
   this.onViewRefreshed = this.onViewRefreshed.bind(this);
 
   this.view.on("ruleview-refreshed", this.onViewRefreshed);
-  this.inspector.selection.on("detached-front", this.onSelected);
+  this.inspector.selection.on("detached-front", this.onDetachedFront);
   this.inspector.selection.on("new-node-front", this.onSelected);
   this.inspector.selection.on("pseudoclass", this.refresh);
   this.inspector.target.on("navigate", this.clearUserProperties);
   this.inspector.ruleViewSideBar.on("ruleview-selected", this.onPanelSelected);
   this.inspector.sidebar.on("ruleview-selected", this.onPanelSelected);
   this.inspector.pageStyle.on("stylesheet-updated", this.refresh);
   this.inspector.walker.on("mutations", this.onMutations);
   this.inspector.walker.on("resize", this.onResized);
@@ -1653,17 +1653,21 @@ RuleViewTool.prototype = {
     if (!this.view) {
       return false;
     }
 
     return this.inspector.isSplitRuleViewEnabled ?
       true : this.inspector.sidebar.getCurrentTabID() == "ruleview";
   },
 
-  onSelected: function(event) {
+  onDetachedFront: function() {
+    this.onSelected(false);
+  },
+
+  onSelected: function(selectElement = true) {
     // Ignore the event if the view has been destroyed, or if it's inactive.
     // But only if the current selection isn't null. If it's been set to null,
     // let the update go through as this is needed to empty the view on
     // navigation.
     if (!this.view) {
       return;
     }
 
@@ -1676,17 +1680,17 @@ RuleViewTool.prototype = {
     this.view.setPageStyle(this.inspector.pageStyle);
 
     if (!this.inspector.selection.isConnected() ||
         !this.inspector.selection.isElementNode()) {
       this.view.selectElement(null);
       return;
     }
 
-    if (!event || event == "new-node-front") {
+    if (selectElement) {
       let done = this.inspector.updating("rule-view");
       this.view.selectElement(this.inspector.selection.nodeFront)
         .then(done, done);
     }
   },
 
   refresh: function() {
     if (this.isSidebarActive()) {
@@ -1732,17 +1736,17 @@ RuleViewTool.prototype = {
    */
   onResized: function() {
     this.refresh();
   },
 
   destroy: function() {
     this.inspector.walker.off("mutations", this.onMutations);
     this.inspector.walker.off("resize", this.onResized);
-    this.inspector.selection.off("detached-front", this.onSelected);
+    this.inspector.selection.off("detached-front", this.onDetachedFront);
     this.inspector.selection.off("pseudoclass", this.refresh);
     this.inspector.selection.off("new-node-front", this.onSelected);
     this.inspector.target.off("navigate", this.clearUserProperties);
     this.inspector.sidebar.off("ruleview-selected", this.onPanelSelected);
     if (this.inspector.pageStyle) {
       this.inspector.pageStyle.off("stylesheet-updated", this.refresh);
     }