Fix appcache/fallback test race exposed by the Blink Scheduler.

The blink scheduler exposed a race where the onnoupdate event could happen
before the iframe has been loaded, causing the test to become flaky. This
fix replaces the use of onnoupdate with an onload event on the iframe.

Also remove linux specific expectation since the linux expected result is
now the same as all other platforms.

BUG=432129

Review URL: https://codereview.chromium.org/720963002

git-svn-id: svn://svn.chromium.org/blink/trunk@185279 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/http/tests/appcache/fallback.html

@@ -120,11 +120,18 @@ function test4()
 
     var ifr = document.createElement("iframe");
     ifr.setAttribute("src", nonexistentURL);
+    ifr.setAttribute("onload", "test5()");
     document.body.appendChild(ifr);
 }
 
+var test5_calls = 0;
+
 function test5()
 {
+    test5_calls++;
+    if (test5_calls == 1) {
+        return;
+    }
     if (!/Hello, World/.test(window.frames[0].document.documentElement.innerHTML)) {
         log("FAIL: Fallback URL was not honored for main resource");
         hadError = true;

third_party/WebKit/LayoutTests/platform/linux/http/tests/appcache/fallback-expected.txt

-Test application cache fallback entries.
-
-Should say SUCCESS:
-
-SUCCESS
-