service worker: Wait for request body blobs to finish construction

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/request-body-blob-worker.js

Index: third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/request-body-blob-worker.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/request-body-blob-worker.js b/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/request-body-blob-worker.js
new file mode 100644
index 0000000000000000000000000000000000000000..8a9c44bab98ee31d2e4c168e78a4c0249822572e
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/request-body-blob-worker.js
@@ -0,0 +1,12 @@
+self.addEventListener('fetch', event => {
+    if (event.request.url.indexOf('?post-with-blob-body') == -1)
+      return;
+    event.respondWith(
+     event.request.text().then(resp => {
+       if (resp.indexOf('it\'s me the blob') == -1)
+         return new Response('fail');
+       if (resp.indexOf('and more blob!') == -1)
+         return new Response('fail');
+       return new Response('Pass');
+     }));
+  });