Reland [wasm] Check the result of Promise::Resolver

The original CL was reverted because regression test used i18n stuff,
which was not available in the no-i18n bot.

The regression test turned out to be flaky, because I cannot even
reproduce the crash now without the fix. I think the reason is that for
the crash to happen a stack check has to fail within the rejection of
a promise. Small changes can cause the stack check to fail somewhere
else. Investigations showed though that the crash should still be
possible. I propose therefore to land the fix now without the
regression test.

Original message:
We check that if we do not get a result, or if we get a negative result,
then there has to be a scheduled exception.

R=clemensh@chromium.org
BUG=chromium:704127

Change-Id: Iaf355249686412a636074a476687413b621aac68
Reviewed-on: https://chromium-review.googlesource.com/464846Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44300}

src/wasm/wasm-js.cc

@@ -148,7 +148,8 @@ void WebAssemblyCompile(const v8::FunctionCallbackInfo<v8::Value>& args) {
   auto bytes = GetFirstArgumentAsBytes(args, &thrower);
   if (thrower.error()) {
     auto maybe = resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
-    CHECK(!maybe.IsNothing());
+    CHECK_IMPLIES(!maybe.FromMaybe(false),
+                  i_isolate->has_scheduled_exception());
     return;
   }
   i::Handle<i::JSPromise> promise = Utils::OpenHandle(*resolver->GetPromise());
@@ -299,7 +300,8 @@ void WebAssemblyInstantiate(const v8::FunctionCallbackInfo<v8::Value>& args) {
         "Argument 0 must be provided and must be either a buffer source or a "
         "WebAssembly.Module object");
     auto maybe = resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
-    CHECK(!maybe.IsNothing());
+    CHECK_IMPLIES(!maybe.FromMaybe(false),
+                  i_isolate->has_scheduled_exception());
     return;
   }
 
@@ -308,14 +310,16 @@ void WebAssemblyInstantiate(const v8::FunctionCallbackInfo<v8::Value>& args) {
     thrower.TypeError(
         "Argument 0 must be a buffer source or a WebAssembly.Module object");
     auto maybe = resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
-    CHECK(!maybe.IsNothing());
+    CHECK_IMPLIES(!maybe.FromMaybe(false),
+                  i_isolate->has_scheduled_exception());
     return;
   }
 
   auto maybe_imports = GetSecondArgumentAsImports(args, &thrower);
   if (thrower.error()) {
     auto maybe = resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
-    CHECK(!maybe.IsNothing());
+    CHECK_IMPLIES(!maybe.FromMaybe(false),
+                  i_isolate->has_scheduled_exception());
     return;
   }
   i::Handle<i::JSPromise> promise = Utils::OpenHandle(*resolver->GetPromise());
@@ -329,7 +333,8 @@ void WebAssemblyInstantiate(const v8::FunctionCallbackInfo<v8::Value>& args) {
     auto bytes = GetFirstArgumentAsBytes(args, &thrower);
     if (thrower.error()) {
       auto maybe = resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
-      CHECK(!maybe.IsNothing());
+      CHECK_IMPLIES(!maybe.FromMaybe(false),
+                    i_isolate->has_scheduled_exception());
       return;
     }
     i::wasm::AsyncCompileAndInstantiate(i_isolate, promise, bytes,

src/wasm/wasm-module.cc

@@ -2609,7 +2609,7 @@ void RejectPromise(Isolate* isolate, ErrorThrower* thrower,
   Handle<Context> context(isolate->context(), isolate);
   auto maybe = resolver->Reject(v8::Utils::ToLocal(context),
                    v8::Utils::ToLocal(thrower->Reify()));
-  CHECK(!maybe.IsNothing());
+  CHECK_IMPLIES(!maybe.FromMaybe(false), isolate->has_scheduled_exception());
 }
 
 void ResolvePromise(Isolate* isolate, Handle<JSPromise> promise,
@@ -2619,7 +2619,7 @@ void ResolvePromise(Isolate* isolate, Handle<JSPromise> promise,
   Handle<Context> context(isolate->context(), isolate);
   auto maybe = resolver->Resolve(v8::Utils::ToLocal(context),
                                  v8::Utils::ToLocal(result));
-  CHECK(!maybe.IsNothing());
+  CHECK_IMPLIES(!maybe.FromMaybe(false), isolate->has_scheduled_exception());
 }
 
 }  // namespace