Add null check for frame when creating WebCore::Performance.

LayoutTests/fast/dom/Window/property-access-on-cached-window-after-frame-removed-and-gced-expected.txt

 CONSOLE WARNING: 'window.webkitStorageInfo' is deprecated. Please use 'navigator.webkitTemporaryStorage' or 'navigator.webkitPersistentStorage' instead.
-Tests property access on a cached DOMWindow after the associated frame is no longer in a web page. Test should not crash and properties should be set to sane defaults.
+Tests property access on a cached DOMWindow after the associated frame is removed from a web page and garbage collected. Test should not crash and properties should be set to sane defaults.
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 
 PASS childWindow.devicePixelRatio is 0
 PASS childWindow.history.length is 0
 PASS childWindow.innerHeight is 0
 PASS childWindow.innerWidth is 0
+FAIL childWindow.jsTestIsAsync should be false (of type boolean). Was undefined (of type undefined).
 PASS childWindow.length is 0
-PASS childWindow.location.href is 'about:blank'
-PASS childWindow.location.origin is 'null'
-PASS childWindow.location.pathname is 'blank'
-PASS childWindow.location.protocol is 'about:'
+FAIL childWindow.location.href should be about:blank (of type string). Was undefined (of type undefined).
+FAIL childWindow.location.origin should be null (of type string). Was undefined (of type undefined).
+FAIL childWindow.location.pathname should be blank (of type string). Was undefined (of type undefined).
+FAIL childWindow.location.protocol should be about: (of type string). Was undefined (of type undefined).
 PASS childWindow.locationbar.visible is false
 PASS childWindow.menubar.visible is false
 PASS childWindow.navigator.appCodeName is window.navigator.appCodeName
 PASS childWindow.navigator.appName is window.navigator.appName
 PASS childWindow.navigator.appVersion is ''
-PASS childWindow.navigator.battery.charging is true
-PASS childWindow.navigator.battery.chargingTime is Infinity
-PASS childWindow.navigator.battery.dischargingTime is Infinity
-PASS childWindow.navigator.battery.level is 1
+FAIL childWindow.navigator.battery.charging should be false. Threw exception TypeError: Cannot read property 'charging' of null
+FAIL childWindow.navigator.battery.chargingTime should be 0. Threw exception TypeError: Cannot read property 'chargingTime' of null
+FAIL childWindow.navigator.battery.dischargingTime should be 0. Threw exception TypeError: Cannot read property 'dischargingTime' of null
+FAIL childWindow.navigator.battery.level should be 0. Threw exception TypeError: Cannot read property 'level' of null
 PASS childWindow.navigator.cookieEnabled is false
 PASS childWindow.navigator.language is window.navigator.language
 PASS childWindow.navigator.onLine is window.navigator.onLine
 PASS childWindow.navigator.platform is window.navigator.platform
 PASS childWindow.navigator.product is window.navigator.product
 PASS childWindow.navigator.productSub is window.navigator.productSub
 PASS childWindow.navigator.userAgent is ''
 PASS childWindow.navigator.vendor is window.navigator.vendor
 FAIL childWindow.offscreenBuffering should be false. Was true.
 PASS childWindow.outerHeight is 0
@@ skipping 17 matching lines @@
 PASS childWindow.screen.pixelDepth is 0
 PASS childWindow.screen.width is 0
 PASS childWindow.scrollbars.visible is false
 PASS childWindow.statusbar.visible is false
 PASS childWindow.styleMedia.type is ''
 PASS childWindow.toolbar.visible is false
 PASS successfullyParsed is true
 
 TEST COMPLETE