Remove implementation of Panels on OSes other than ChromeOS.

chrome/test/data/extensions/api_test/window_open/panel_browsing_instance/background.js

-// Copyright 2015 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.
-
-// To see chrome.test.log messages execute the test like this:
-// $ out/gn/browser_tests --gtest_filter=*PanelTest* --vmodule=test_api=1
-chrome.test.log('executing background.js ...');
-
-var oldNumberOfTabs;
-var expectedWindowType;
-chrome.test.runTests([
-  function testPanelBrowsingInstance() {
-    chrome.test.log('counting all the tabs (before window.open) ...');
-    chrome.tabs.query({}, function(tabs) {
-      oldNumberOfTabs = tabs.length;
-      chrome.test.log('oldNumberOfTabs = ' + oldNumberOfTabs);
-
-      // Note that the background-subframe has to be navigated to foo.com,
-      // because otherwise we would get the following error when calling
-      // window.open from panel-subframe.js:
-      //   Unsafe JavaScript attempt to initiate navigation for frame with URL
-      //   'about:blank' from frame with URL
-      //   'http://foo.com:41191/extensions/.../panel-subframe.html'.  The frame
-      //   attempting navigation is neither same-origin with the target, nor is
-      //   it the target's parent or opener.
-      chrome.test.getConfig(function(config) {
-        expectedWindowType = config.customArg;
-
-        var baseUri = 'http://foo.com:' + config.testServer.port +
-            '/extensions/api_test/window_open/panel_browsing_instance/';
-
-        chrome.test.log('navigating background-subframe ...');
-        var subframe = document.getElementById('background-subframe-id');
-        subframe.src = baseUri +
-            'background-subframe.html?extensionId=' + chrome.runtime.id;
-
-        // background-subframe.js will send a message back to us -
-        // backgroundSubframeNavigated - we will continue execution
-        // in the callback below.
-      });
-    });
-  }
-]);
-
-chrome.runtime.onMessageExternal.addListener(
-  function(request, sender, sendResponse) {
-    if (request.backgroundSubframeNavigated) {
-      chrome.test.log('got callback from background-subframe.js ...');
-      chrome.test.log('creating the panel window ...');
-      chrome.windows.create(
-          { 'url': chrome.extension.getURL('panel.html'), 'type': 'panel' },
-          function(win) {
-            chrome.test.assertEq(expectedWindowType, win.type);
-          });
-
-      // panel.js will navigate panel-subframe and then panel-subframe.js will
-      // call window.open and send a message back to us (windowOpened) - we will
-      // continue execution below.
-    } else if (request.windowOpened) {
-      chrome.test.log('got callback from panel-subframe.js ...');
-      chrome.test.log('counting all the tabs (after window.open) ...');
-      chrome.tabs.query({}, function(tabs) {
-        var newNumberOfTabs = tabs.length;
-        chrome.test.log('newNumberOfTabs = ' + newNumberOfTabs);
-
-        switch (expectedWindowType) {
-          case 'panel':
-            chrome.test.assertEq(newNumberOfTabs, oldNumberOfTabs);
-            break;
-          case 'popup':
-            chrome.test.assertEq(newNumberOfTabs, oldNumberOfTabs + 1);
-            break;
-          default:
-            // Unexpected expected window type.
-            chrome.test.fail();
-        }
-        chrome.test.notifyPass();
-      });
-    }
-  });
-
-