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/ScriptValue.h"
+#include "bindings/core/v8/ToV8.h"
+#include "core/CoreExport.h"
+#include <v8.h>
+
+namespace blink {
+
+class CORE_EXPORT ReadableStreamController {
+public:
+    explicit ReadableStreamController(ScriptValue stream) : m_stream(stream)
+    {
+    }
+
+    void close()
+    {
+        if (m_stream.isEmpty())
+            return;
+
+        ScriptState::Scope scope(m_stream.scriptState());
+
+        auto func = m_stream.scriptState()->getFromExtrasExports("CloseReadableStream").v8Value().As<v8::Function>();
+
+        auto undefined = v8::Undefined(m_stream.isolate());
+        v8::Local<v8::Value> args[] = { m_stream.v8Value() };
+        auto result = func->Call(m_stream.context(), undefined, arraysize(args), args);
+
+        ASSERT(!result.IsEmpty());
+        m_stream.clear();
+    }
+
+    double desiredSize() const
+    {
+        if (m_stream.isEmpty())
+            return 0;
+
+        ScriptState::Scope scope(m_stream.scriptState());
+
+        auto func = m_stream.scriptState()->getFromExtrasExports("GetReadableStreamDesiredSize").v8Value()
+            .As<v8::Function>();
+
+        auto undefined = v8::Undefined(m_stream.isolate());
+        v8::Local<v8::Value> args[] = { m_stream.v8Value() };
+        auto result = func->Call(m_stream.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_stream.scriptState());
+
+        auto func = m_stream.scriptState()->getFromExtrasExports("EnqueueInReadableStream").v8Value()
+            .As<v8::Function>();
+
+        auto chunkForV8 = toV8(chunk, m_stream.context()->Global(), m_stream.isolate());
+        auto undefined = v8::Undefined(m_stream.isolate());
+        v8::Local<v8::Value> args[] = { m_stream.v8Value(), chunkForV8 };
+
+        auto result = func->Call(m_stream.context(), undefined, arraysize(args), args);
+
+        ASSERT(!result.IsEmpty());
+    }
+
+    template<typename ErrorType>
+    void error(ErrorType e)
+    {
+        if (m_stream.isEmpty())
+            return;
+
+        ScriptState::Scope scope(m_stream.scriptState());
+
+        auto func = m_stream.scriptState()->getFromExtrasExports("ErrorReadableStream").v8Value().As<v8::Function>();
+
+        auto errorForV8 = toV8(e, m_stream.context()->Global(), m_stream.isolate());
+        auto undefined = v8::Undefined(m_stream.isolate());
+        v8::Local<v8::Value> args[] = { m_stream.v8Value(), errorForV8 };
+        auto result = func->Call(m_stream.context(), undefined, arraysize(args), args);
+
+        ASSERT(!result.IsEmpty());
+        m_stream.clear();
+    }
+
+private:
+    ScriptValue m_stream;
+};
+
+} // namespace blink
+
+#endif // ReadableStreamController_h