[ServiceWorker] Set FetchEvent's request's headers' guard to immutable

The spec of ServiceWorker was changed.
https://github.com/slightlyoff/ServiceWorker/issues/559
https://github.com/slightlyoff/ServiceWorker/commit/fe2cd64e9d84c316fc02b7c29648b0c712402746

BUG=N/A
TEST=http/tests/serviceworker/

Review URL: https://codereview.chromium.org/723963003

git-svn-id: svn://svn.chromium.org/blink/trunk@185416 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/http/tests/serviceworker/request-end-to-end.html

@@ -41,7 +41,8 @@ t.step(function() {
     function onMessage(event) {
         assert_equals(
             event.data.url,
-            location.href.substring(0, location.href.lastIndexOf('/') + 1) + scope,
+            location.href.substring(0, location.href.lastIndexOf('/') + 1) +
+            scope,
             'request.url should be passed to onfetch event.');
         assert_equals(event.data.method, 'GET',
                       'request.method should be passed to onfetch event.');
@@ -49,6 +50,9 @@ t.step(function() {
                       'request.referrer should be passed to onfetch event.');
         assert_equals(event.data.headers['user-agent'], navigator.userAgent,
                       'User-Agent header should be passed to onfetch event.')
+        assert_equals(event.data.errorNameWhileAppendingHeader, 'TypeError',
+                      'Appending a new header to the request must throw a ' +
+                      'TypeError.')
         service_worker_unregister_and_done(t, scope);
     }
 });

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/request-end-to-end-worker.js

@@ -13,11 +13,18 @@ onfetch = function(e) {
     var key = header[0], value = header[1];
     headers[key] = value;
   }
+  var errorNameWhileAddingHeader = '';
+  try {
+    e.request.headers.append('Test-Header', 'TestValue');
+  } catch (e) {
+    errorNameWhileAppendingHeader = e.name;
+  }
   port.postMessage({
       url: e.request.url,
       method: e.request.method,
       referrer: e.request.referrer,
       headers: headers,
-      headerSize: e.request.headers.size
+      headerSize: e.request.headers.size,
+      errorNameWhileAppendingHeader: errorNameWhileAppendingHeader
     });
 };

third_party/WebKit/Source/web/ServiceWorkerGlobalScopeProxy.cpp

@@ -45,6 +45,7 @@
 #include "modules/push_messaging/PushEvent.h"
 #include "modules/serviceworkers/ExtendableEvent.h"
 #include "modules/serviceworkers/FetchEvent.h"
+#include "modules/serviceworkers/Headers.h"
 #include "modules/serviceworkers/InstallEvent.h"
 #include "modules/serviceworkers/ServiceWorkerGlobalScope.h"
 #include "modules/serviceworkers/WaitUntilObserver.h"
@@ -87,6 +88,7 @@ void ServiceWorkerGlobalScopeProxy::dispatchFetchEvent(int eventID, const WebSer
     }
 
     Request* request = Request::create(m_workerGlobalScope, webRequest);
+    request->headers()->setGuard(Headers::ImmutableGuard);
     RefPtrWillBeRawPtr<FetchEvent> fetchEvent(FetchEvent::create(observer, request));
     fetchEvent->setIsReload(webRequest.isReload());
     m_workerGlobalScope->dispatchEvent(fetchEvent.release());