Bug 1272857 - Fix some tree performance tests to read/write element.style.marginInlineStart instead of just element.marginInlineStart. r=gregtatum

This is a followup to bug 1111440.

MozReview-Commit-ID: BHCexWmrHoT

devtools/client/performance/test/browser_perf-tree-abstract-01.js

@@ -38,7 +38,7 @@ add_task(function* () {
     "The root node has the correct parent.");
   is(treeRoot.level, 0,
     "The root node has the correct level.");
-  is(treeRoot.target.marginInlineStart, "0px",
+  is(treeRoot.target.style.marginInlineStart, "0px",
     "The root node's indentation is correct.");
   is(treeRoot.target.textContent, "root",
     "The root node's text contents are correct.");
@@ -77,7 +77,7 @@ add_task(function* () {
     "The 'foo' node has the correct parent.");
   is(fooItem.level, 1,
     "The 'foo' node has the correct level.");
-  is(fooItem.target.marginInlineStart, "10px",
+  is(fooItem.target.style.marginInlineStart, "10px",
     "The 'foo' node's indentation is correct.");
   is(fooItem.target.textContent, "foo",
     "The 'foo' node's text contents are correct.");
@@ -90,7 +90,7 @@ add_task(function* () {
     "The 'bar' node has the correct parent.");
   is(barItem.level, 1,
     "The 'bar' node has the correct level.");
-  is(barItem.target.marginInlineStart, "10px",
+  is(barItem.target.style.marginInlineStart, "10px",
     "The 'bar' node's indentation is correct.");
   is(barItem.target.textContent, "bar",
     "The 'bar' node's text contents are correct.");
@@ -143,7 +143,7 @@ add_task(function* () {
     "The 'baz' node has the correct parent.");
   is(bazItem.level, 2,
     "The 'baz' node has the correct level.");
-  is(bazItem.target.marginInlineStart, "20px",
+  is(bazItem.target.style.marginInlineStart, "20px",
     "The 'baz' node's indentation is correct.");
   is(bazItem.target.textContent, "baz",
     "The 'baz' node's text contents are correct.");

devtools/client/performance/test/helpers/synth-utils.js

@@ -65,7 +65,7 @@ exports.synthesizeCustomTreeClass = () => {
   MyCustomTreeItem.prototype = Heritage.extend(AbstractTreeItem.prototype, {
     _displaySelf: function (document, arrowNode) {
       let node = document.createElement("hbox");
-      node.marginInlineStart = (this.level * 10) + "px";
+      node.style.marginInlineStart = (this.level * 10) + "px";
       node.appendChild(arrowNode);
       node.appendChild(document.createTextNode(this.itemDataSrc.label));
       return node;

devtools/client/shared/widgets/AbstractTreeItem.jsm

@@ -50,7 +50,7 @@ this.EXPORTED_SYMBOLS = ["AbstractTreeItem"];
  *     ...
  *     // Use `this.itemDataSrc` to customize the tree item and
  *     // `this.level` to calculate the indentation.
- *     node.marginInlineStart = (this.level * 10) + "px";
+ *     node.style.marginInlineStart = (this.level * 10) + "px";
  *     node.appendChild(document.createTextNode(this.itemDataSrc.label));
  *     ...
  *     return node;