DevTools: Made id unique across different remote browsers

chrome/test/data/webui/inspect_ui_test.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 function waitForElements(selector, populateFunctionName, callback) {
   var elements = document.querySelectorAll(selector);
   if (elements.length) {
     callback(elements);
     return;
   }
@@ skipping 48 matching lines @@
 
     var chromeBrowser = findByContentSubstring(
        browsers, 'Chrome (32.0.1679.0)', '.browser-name');
     expectNotEquals(undefined, chromeBrowser);
 
     var chromePages = chromeBrowser.querySelectorAll('.pages');
     var chromiumPage = findByContentSubstring(
        chromePages, 'http://www.chromium.org/', '.url');
     expectNotEquals(undefined, chromiumPage);
 
+    var pageById = {};
+    Array.prototype.forEach.call(devices, function (device) {
+      var pages = device.querySelectorAll('.row');
+      Array.prototype.forEach.call(pages, function (page) {
+        expectEquals(undefined, pageById[page.targetId]);
+        pageById[page.targetId] = page;
+      });
+    });
+
     var webView = findByContentSubstring(
        browsers, 'WebView in com.sample.feed (4.0)', '.browser-name');
     expectNotEquals(undefined, webView);
 
     testDone();
   });
 }