[wasm] Always restore context in OnFinishedCompile

The callback to AsyncStreamingProcessor::OnFinishedStream would
call into v8 internals without restoring the current context if
the processed module had no code. Instead, now always restore the
context before doing any finishing work.

Bug: chromium:915493
Change-Id: Ib779df81301ad1e3597515a4173c9a57efc593ac
Reviewed-on: https://chromium-review.googlesource.com/c/1397672Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58612}

src/wasm/module-compiler.cc

@@ -3031,6 +3031,13 @@ void AsyncStreamingProcessor::OnFinishedStream(OwnedVector<uint8_t> bytes) {
     FinishAsyncCompileJobWithError(std::move(result));
     return;
   }
+  // We have to open a HandleScope and prepare the Context for
+  // PrepareRuntimeObjects and FinishCompile as this is a callback from the
+  // embedder.
+  HandleScope scope(job_->isolate_);
+  SaveContext saved_context(job_->isolate_);
+  job_->isolate_->set_context(*job_->native_context_);
+
   bool needs_finish = job_->DecrementAndCheckFinisherCount();
   if (job_->native_module_ == nullptr) {
     // We are processing a WebAssembly module without code section. Create the
@@ -3041,9 +3048,6 @@ void AsyncStreamingProcessor::OnFinishedStream(OwnedVector<uint8_t> bytes) {
   job_->wire_bytes_ = ModuleWireBytes(bytes.as_vector());
   job_->native_module_->SetWireBytes(std::move(bytes));
   if (needs_finish) {
-    HandleScope scope(job_->isolate_);
-    SaveContext saved_context(job_->isolate_);
-    job_->isolate_->set_context(*job_->native_context_);
     job_->FinishCompile(true);
   }
 }