Implement HTMLMediaElement::srcObject.

Source/core/html/MediaProvider.cpp

+// Copyright 2014 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.
+
+#include "config.h"
+#include "core/html/MediaProvider.h"
+
+#include "wtf/HashMap.h"
+#include "wtf/MainThread.h"
+#include "wtf/text/StringHash.h"
+
+namespace blink {
+
+class MediaProviderConverterContainer {
+public:
+    static MediaProviderConverterContainer& container();
+
+    void registerMediaProviderConverter(const String& interfaceName, const MediaProvider::Converter&);
+    virtual MediaProvider* convert(const ScriptValue&);
+
+private:
+    HashMap<String, MediaProvider::Converter> m_converters;
+};
+
+MediaProviderConverterContainer& MediaProviderConverterContainer::container()
+{
+    ASSERT(isMainThread());
+    DEFINE_STATIC_LOCAL(MediaProviderConverterContainer, instance, ());
+    return instance;
+}
+
+void MediaProviderConverterContainer::registerMediaProviderConverter(const String& interfaceName, const MediaProvider::Converter& converter)
+{
+    if (m_converters.get(interfaceName).isNull())
+        m_converters.set(interfaceName, converter);
+}
+
+MediaProvider* MediaProviderConverterContainer::convert(const ScriptValue& value)
+{
+    for (HashMap<String, MediaProvider::Converter>::iterator it = m_converters.begin(); it != m_converters.end(); ++it) {
+        MediaProvider* provider = (it->value)(value);
+        if (provider)
+            return provider;
+    }
+    return nullptr;
+}
+
+MediaProvider::MediaProvider(const String& interfaceName, const Converter& converter)
+{
+    MediaProviderConverterContainer& container = MediaProviderConverterContainer::container();
+    container.registerMediaProviderConverter(interfaceName, converter);

[haraken, 2014/09/20 08:52:20]

Don't we need to unregister the convert at some point (e.g., when the
MediaProvider gets destructed)?

[perkj_chrome, 2014/09/24 11:39:38]

I don't think so since what we register is the static converter to be able to
convert all instances of MediaStreams to a MediaProviders. 
The purpose of this is to break the dependency from core to modules/mediastream

+}
+
+MediaProvider* MediaProvider::convert(const ScriptValue& value)
+{
+    MediaProviderConverterContainer& container = MediaProviderConverterContainer::container();
+    return container.convert(value);
+}
+
+} // namespace blink