Change return type of tee() to sequence<ReadableStream> in WebIDL

In an effort to change the blink implementation of readable streams to
better match the Web IDL descriptions in the Streams API Standard, this
CL changes the return type of tee() from |any| to
|sequence<ReadableStream> in readable_stream.idl, and |ScriptValue| to
|HeapVector<Member<ReadableStream>>| in readable_stream.cc. This allows
the code to be slightly simpler as well within
CallTeeAndReturnBranchArray() in the ReadableStream class.

Bug: 1093862
Change-Id: I273e9fa01c5601c578753952c1c0a4b5f8db0fd6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2520638Reviewed-by: Adam Rice <ricea@chromium.org>
Commit-Queue: Nidhi Jaju <nidhijaju@google.com>
Cr-Commit-Position: refs/heads/master@{#824698}

third_party/blink/renderer/core/streams/readable_stream.cc

@@ -1316,8 +1316,9 @@ ScriptPromise ReadableStream::pipeTo(ScriptState* script_state,
   return PipeTo(script_state, this, destination, pipe_options);
 }
 
-ScriptValue ReadableStream::tee(ScriptState* script_state,
-                                ExceptionState& exception_state) {
+HeapVector<Member<ReadableStream>> ReadableStream::tee(
+    ScriptState* script_state,
+    ExceptionState& exception_state) {
   return CallTeeAndReturnBranchArray(script_state, this, exception_state);
 }
 
@@ -1808,12 +1809,11 @@ int ReadableStream::GetNumReadRequests(const ReadableStream* stream) {
 // TODO(ricea): Functions for transferable streams.
 //
 
-ScriptValue ReadableStream::CallTeeAndReturnBranchArray(
+HeapVector<Member<ReadableStream>> ReadableStream::CallTeeAndReturnBranchArray(
     ScriptState* script_state,
     ReadableStream* readable,
     ExceptionState& exception_state) {
   // https://streams.spec.whatwg.org/#rs-tee
-  v8::Isolate* isolate = script_state->GetIsolate();
   ReadableStream* branch1 = nullptr;
   ReadableStream* branch2 = nullptr;
 
@@ -1821,35 +1821,12 @@ ScriptValue ReadableStream::CallTeeAndReturnBranchArray(
   readable->Tee(script_state, &branch1, &branch2, exception_state);
 
   if (!branch1 || !branch2)
-    return ScriptValue();
+    return HeapVector<Member<ReadableStream>>();
 
   DCHECK(!exception_state.HadException());
 
   // 3. Return ! CreateArrayFromList(branches).
-  v8::TryCatch block(isolate);
-  v8::Local<v8::Context> context = script_state->GetContext();
-  v8::Local<v8::Array> array = v8::Array::New(isolate, 2);
-  v8::Local<v8::Object> global = context->Global();
-
-  v8::Local<v8::Value> v8_branch1 = ToV8(branch1, global, isolate);
-  if (v8_branch1.IsEmpty()) {
-    exception_state.RethrowV8Exception(block.Exception());
-    return ScriptValue();
-  }
-  v8::Local<v8::Value> v8_branch2 = ToV8(branch2, global, isolate);
-  if (v8_branch1.IsEmpty()) {
-    exception_state.RethrowV8Exception(block.Exception());
-    return ScriptValue();
-  }
-  if (array->Set(context, V8String(isolate, "0"), v8_branch1).IsNothing()) {
-    exception_state.RethrowV8Exception(block.Exception());
-    return ScriptValue();
-  }
-  if (array->Set(context, V8String(isolate, "1"), v8_branch2).IsNothing()) {
-    exception_state.RethrowV8Exception(block.Exception());
-    return ScriptValue();
-  }
-  return ScriptValue(script_state->GetIsolate(), array);
+  return HeapVector<Member<ReadableStream>>({branch1, branch2});
 }
 
 }  // namespace blink

third_party/blink/renderer/core/streams/readable_stream.h

@@ -138,7 +138,7 @@ class CORE_EXPORT ReadableStream : public ScriptWrappable {
                        ExceptionState&);
 
   // https://streams.spec.whatwg.org/#rs-tee
-  ScriptValue tee(ScriptState*, ExceptionState&);
+  HeapVector<Member<ReadableStream>> tee(ScriptState*, ExceptionState&);
 
   // TODO(domenic): cloneForBranch2 argument from spec not supported yet
   void Tee(ScriptState*,
@@ -272,7 +272,7 @@ class CORE_EXPORT ReadableStream : public ScriptWrappable {
 
   // Calls Tee() on |readable|, converts the two branches to a JavaScript array
   // and returns them.
-  static ScriptValue CallTeeAndReturnBranchArray(
+  static HeapVector<Member<ReadableStream>> CallTeeAndReturnBranchArray(
       ScriptState* script_state,
       ReadableStream* readable,
       ExceptionState& exception_state);

third_party/blink/renderer/core/streams/readable_stream.idl

@@ -18,5 +18,5 @@ enum ReadableStreamReaderMode { "byob" };
         ReadableWritablePair transform, optional StreamPipeOptions options);
     [RaisesException, CallWith=ScriptState, MeasureAs=ReadableStreamPipeTo] Promise<any> pipeTo(
         WritableStream destination, optional StreamPipeOptions options);
-    [RaisesException, CallWith=ScriptState] any tee();
+    [RaisesException, CallWith=ScriptState] sequence<ReadableStream> tee();
 };