Fire load event for link modulepreload with non-fetch errors

According to the spec comment, load events (instead of error events)
should be fired for modules with non-fetch errors such as parse errors.

Bug: 740886, 763597
Change-Id: I6074b36631e1299b90d52bc01e42c5ddeb957b31
Reviewed-on: https://chromium-review.googlesource.com/802251Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Kunihiko Sakamoto <ksakamoto@chromium.org>
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521726}

third_party/WebKit/LayoutTests/external/wpt/preload/modulepreload.html

@@ -71,7 +71,7 @@ promise_test(function(t) {
     var link = document.createElement('link');
     link.rel = 'modulepreload';
     link.href = 'resources/syntax-error.js';
-    return attachAndWaitForError(link);
+    return attachAndWaitForLoad(link);
 }, 'link rel=modulepreload for a module with syntax error');
 
 promise_test(function(t) {

third_party/WebKit/Source/core/loader/LinkLoader.cpp

@@ -146,7 +146,7 @@ void LinkLoader::NotifyModuleLoadFinished(ModuleScript* module) {
   // Step 11. "If result is null, fire an event named error at the link element,
   // and return." [spec text]
   // Step 12. "Fire an event named load at the link element." [spec text]
-  if (!module || module->IsErrored())
+  if (!module)
     client_->LinkLoadingErrored();
   else
     client_->LinkLoaded();