[wasm] Fix and extend comments on JS API

R=ahaas@chromium.org

Bug: v8:9810
Change-Id: I9f6d13445c8c577256cabe070f9082d041af3a2d
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1903437Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64841}

src/wasm/wasm-js.cc

@@ -565,7 +565,8 @@ void WasmStreamingPromiseFailedCallback(
   streaming->Abort(args[0]);
 }
 
-// WebAssembly.compileStreaming(Promise<Response>) -> Promise
+// WebAssembly.compileStreaming(Response | Promise<Response>)
+//   -> Promise<WebAssembly.Module>
 void WebAssemblyCompileStreaming(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();
@@ -822,6 +823,9 @@ void WebAssemblyInstance(const v8::FunctionCallbackInfo<v8::Value>& args) {
   }
 }
 
+// WebAssembly.instantiateStreaming(Response | Promise<Response> [, imports])
+//   -> Promise<ResultObject>
+// (where ResultObject has a "module" and an "instance" field)
 void WebAssemblyInstantiateStreaming(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();