Enable chrome.automation.getDesktop on all aura platforms.

chrome/test/data/extensions/api_test/automation/tests/desktop/common.js

Index: chrome/test/data/extensions/api_test/automation/tests/desktop/common.js
diff --git a/chrome/test/data/extensions/api_test/automation/tests/desktop/common.js b/chrome/test/data/extensions/api_test/automation/tests/desktop/common.js
index a6d3d9afb09ae040e9b16185b7e4a3c46e37654d..7a2b9030472ac9587823a04673312e3bca9fc306 100644
--- a/chrome/test/data/extensions/api_test/automation/tests/desktop/common.js
+++ b/chrome/test/data/extensions/api_test/automation/tests/desktop/common.js
@@ -42,14 +42,28 @@ function runWithDocument(docString, callback) {
 
 function setupAndRunTests(allTests, opt_docString) {
   function runTestInternal() {
-    chrome.automation.getDesktop(function(rootNodeArg) {
-      rootNode = rootNodeArg;
-      chrome.test.runTests(allTests);
-    });
+    chrome.test.runTests(allTests);
   }
 
-  if (opt_docString)
-    runWithDocument(opt_docString, runTestInternal);
-  else
-    runTestInternal();
+  chrome.automation.getDesktop(function(rootNodeArg) {
+    rootNode = rootNodeArg;
+
+    // Only run the test when the window containing the new tab loads.
+    rootNodeArg.addEventListener(
+        chrome.automation.EventType.childrenChanged,
+        function(evt) {
+          var subroot = evt.target.firstChild;
+          if (!opt_docString || !subroot)
+            return;
+
+          if (subroot.role == 'rootWebArea' &&
+              subroot.attributes.docUrl.indexOf(opt_docString) != -1)
+            runTestInternal();
+        },
+        true);
+    if (opt_docString)
+      runWithDocument(opt_docString, null);
+    else
+      runTestInternal();
+  });
 }