Add methods for creating V8 extras-based ReadableStreams from C++

Source/core/streams/ReadableStreamController.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ReadableStreamController_h
+#define ReadableStreamController_h
+
+#include "bindings/core/v8/ScopedPersistent.h"
+#include "bindings/core/v8/ScriptValue.h"
+#include "bindings/core/v8/ToV8.h"
+#include "core/CoreExport.h"
+#include "platform/heap/Handle.h"
+#include <v8.h>
+
+namespace blink {
+
+class CORE_EXPORT ReadableStreamController final : public GarbageCollectedFinalized<ReadableStreamController> {
+public:
+    DEFINE_INLINE_TRACE() { }
+
+    explicit ReadableStreamController(ScriptValue stream)
+        : m_scriptState(stream.scriptState())
+        , m_stream(stream.isolate(), stream.v8Value())
+    {
+        m_stream.setWeak(&m_stream, ReadableStreamController::streamWeakCallback);
+    }
+
+    // Users of the ReadableStreamController can call this to note that the stream has been canceled and thus they
+    // don't anticipate using the ReadableStreamController anymore. (close/desiredSize/enqueue/error will become no-ops
+    // afterward.)
+    void noteHasBeenCanceled()
+    {
+        m_stream.clear();
+    }
+
+    bool isActive() const
+    {
+        return !m_stream.isEmpty();
+    }
+
+    void close()
+    {
+        if (m_stream.isEmpty())
+            return;
+
+        ScriptState::Scope scope(m_scriptState);
+
+        // TODO: should we be storing these somewhere so that we don't need to get the v8::Local<v8::Function> every
+        // time?
+        auto func = m_scriptState->getFromExtrasExports("CloseReadableStream").v8Value().As<v8::Function>();
+
+        auto isolate = m_scriptState->isolate();
+        auto context = m_scriptState->context();
+        auto undefined = v8::Undefined(isolate);
+        v8::Local<v8::Value> args[] = { m_stream.newLocal(isolate) };
+        auto result = func->Call(context, undefined, arraysize(args), args);
+
+        ASSERT_UNUSED(result, !result.IsEmpty());
+        m_stream.clear();
+    }
+
+    double desiredSize() const
+    {
+        if (m_stream.isEmpty())
+            return 0;
+
+        ScriptState::Scope scope(m_scriptState);
+
+        auto func = m_scriptState->getFromExtrasExports("GetReadableStreamDesiredSize").v8Value().As<v8::Function>();
+
+        auto isolate = m_scriptState->isolate();
+        auto context = m_scriptState->context();
+        auto undefined = v8::Undefined(isolate);
+        v8::Local<v8::Value> args[] = { m_stream.newLocal(isolate) };
+        auto result = func->Call(context, undefined, arraysize(args), args).ToLocalChecked();
+
+        return result.As<v8::Number>()->Value();
+    }
+
+    template<typename ChunkType>
+    void enqueue(ChunkType chunk) const
+    {
+        if (m_stream.isEmpty())
+            return;
+
+        ScriptState::Scope scope(m_scriptState);
+
+        auto func = m_scriptState->getFromExtrasExports("EnqueueInReadableStream").v8Value().As<v8::Function>();
+
+        auto isolate = m_scriptState->isolate();
+        auto context = m_scriptState->context();
+        auto undefined = v8::Undefined(isolate);
+        auto chunkForV8 = toV8(chunk, context->Global(), isolate);
+        v8::Local<v8::Value> args[] = { m_stream.newLocal(isolate), chunkForV8 };
+
+        auto result = func->Call(context, undefined, arraysize(args), args);
+
+        ASSERT_UNUSED(result, !result.IsEmpty());
+    }
+
+    template<typename ErrorType>
+    void error(ErrorType e)
+    {
+        if (m_stream.isEmpty())
+            return;
+
+        ScriptState::Scope scope(m_scriptState);
+
+        auto func = m_scriptState->getFromExtrasExports("ErrorReadableStream").v8Value().As<v8::Function>();
+
+        auto isolate = m_scriptState->isolate();
+        auto context = m_scriptState->context();
+        auto undefined = v8::Undefined(isolate);
+        auto errorForV8 = toV8(e, context->Global(), isolate);
+        v8::Local<v8::Value> args[] = { m_stream.newLocal(isolate), errorForV8 };
+        auto result = func->Call(context, undefined, arraysize(args), args);
+
+        ASSERT_UNUSED(result, !result.IsEmpty());
+        m_stream.clear();
+    }
+
+private:
+    static void streamWeakCallback(const v8::WeakCallbackInfo<ScopedPersistent<v8::Value>>& weakInfo)
+    {
+        weakInfo.GetParameter()->clear();
+    }
+
+    ScopedPersistent<v8::Value> m_stream;
+    ScriptState* m_scriptState;
+};
+
+} // namespace blink
+
+#endif // ReadableStreamController_h