Handle XULDocument in the Document rep.

Add a stub and a test to make sure we don't regress this.
Fixes #933.
And fixes https://bugzilla.mozilla.org/show_bug.cgi\?id\=1438454 .

Author: nchevobbe

packages/devtools-reps/src/reps/document.js

@@ -61,7 +61,8 @@ function supportsObject(object, noGrip = false) {
     return false;
   }
 
-  return (object.preview && getGripType(object, noGrip) == "HTMLDocument");
+  const type = getGripType(object, noGrip);
+  return (object.preview && (type === "HTMLDocument" || type === "XULDocument"));
 }
 
 // Exports from this module

packages/devtools-reps/src/reps/stubs/document.js

@@ -34,4 +34,21 @@ stubs.set("Location-less Document", {
   }
 });
 
+stubs.set("XULDocument", {
+  "type": "object",
+  "actor": "server1.conn0.obj434",
+  "class": "XULDocument",
+  "extensible": true,
+  "frozen": false,
+  "sealed": false,
+  "ownPropertyLength": 1,
+  "preview": {
+    "kind": "DOMNode",
+    "nodeType": 9,
+    "nodeName": "#document",
+    "isConnected": true,
+    "location": "chrome://browser/content/browser.xul"
+  }
+});
+
 module.exports = stubs;

packages/devtools-reps/src/reps/tests/document.js

@@ -14,9 +14,9 @@ const {
 
 const { Document } = REPS;
 const stubs = require("../stubs/document");
-const stub = stubs.get("Document");
 
 describe("Document", () => {
+  const stub = stubs.get("Document");
   it("correctly selects Document Rep", () => {
     expect(getRep(stub)).toBe(Document.rep);
   });
@@ -39,3 +39,20 @@ describe("Document", () => {
     expect(renderedComponent.text()).toEqual("HTMLDocument");
   });
 });
+
+describe("XULDocument", () => {
+  const stub = stubs.get("XULDocument");
+  it("correctly selects Document Rep", () => {
+    expect(getRep(stub)).toBe(Document.rep);
+  });
+
+  it("renders with expected text content", () => {
+    const renderedComponent = shallow(Document.rep({
+      object: stub
+    }));
+
+    expect(renderedComponent.text())
+      .toEqual("XULDocument chrome://browser/content/browser.xul");
+    expectActorAttribute(renderedComponent, stub.actor);
+  });
+});