Set explicit_timeout to true in nested window test environment in blob URL tests.

This way the tests will timeout when the outer window decides time has
expired, rather than let the nested window decide it earlier.

This mimics the behavior of fetch_tests_from_worker, since
WorkerTestEnvironment always behaves as if explicit_timeout is set to
true.

This should fix spurious timeouts of this test that aren't detected as
timeouts by our test runner (and specifically cases where we don't
actually consider the test as timed out).

Bug: 801078
Change-Id: I3a884bd746afcefd5cbe5008db7df4a609eb0044
Reviewed-on: https://chromium-review.googlesource.com/865002
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529500}
diff --git a/FileAPI/url/sandboxed-iframe.html b/FileAPI/url/sandboxed-iframe.html
index e7a8a15..3eca08d 100644
--- a/FileAPI/url/sandboxed-iframe.html
+++ b/FileAPI/url/sandboxed-iframe.html
@@ -9,7 +9,6 @@
 <script>
 
 const iframe_scripts = [
-  '/resources/testharness.js',
   'resources/fetch-tests.js',
   'url-format.any.js',
   'url-with-xhr.any.js',
@@ -18,6 +17,8 @@
 ];
 
 let html = '<!doctype html>\n<meta charset="utf-8">\n<body>\n';
+html = html + '<script src="/resources/testharness.js"></' + 'script>\n';
+html = html + '<script>setup({"explicit_timeout": true});</' + 'script>\n';
 for (const script of iframe_scripts)
   html = html + '<script src="' + script + '"></' + 'script>\n';
 
@@ -27,4 +28,4 @@
 
 fetch_tests_from_window(frame.contentWindow);
 
-</script>
\ No newline at end of file
+</script>