Reland: Generate separate files for union type containers

third_party/WebKit/Source/bindings/templates/union.h

-{% include 'copyright_block.txt' %}
-#ifndef {{macro_guard}}
-#define {{macro_guard}}
-
-{% for filename in header_includes %}
-#include "{{filename}}"
-{% endfor %}
-
-namespace blink {
-
-{% for decl in header_forward_decls %}
-class {{decl}};
-{% endfor %}
-
-{% for container in containers %}
-class {{exported}}{{container.cpp_class}} final {
-    DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
-public:
-    {{container.cpp_class}}();
-    bool isNull() const { return m_type == SpecificTypeNone; }
-
-    {% for member in container.members %}
-    bool is{{member.type_name}}() const { return m_type == {{member.specific_type_enum}}; }
-    {{member.rvalue_cpp_type}} getAs{{member.type_name}}() const;
-    void set{{member.type_name}}({{member.rvalue_cpp_type}});
-    static {{container.cpp_class}} from{{member.type_name}}({{member.rvalue_cpp_type}});
-
-    {% endfor %}
-    {{container.cpp_class}}(const {{container.cpp_class}}&);
-    ~{{container.cpp_class}}();
-    {{container.cpp_class}}& operator=(const {{container.cpp_class}}&);
-    DECLARE_TRACE();
-
-private:
-    enum SpecificTypes {
-        SpecificTypeNone,
-        {% for member in container.members %}
-        {{member.specific_type_enum}},
-        {% endfor %}
-    };
-    SpecificTypes m_type;
-
-    {% for member in container.members %}
-    {{member.cpp_type}} m_{{member.cpp_name}};
-    {% endfor %}
-
-    friend {{exported}}v8::Local<v8::Value> toV8(const {{container.cpp_class}}&, v8::Local<v8::Object>, v8::Isolate*);
-};
-
-class V8{{container.cpp_class}} final {
-public:
-    {{exported}}static void toImpl(v8::Isolate*, v8::Local<v8::Value>, {{container.cpp_class}}&, UnionTypeConversionMode, ExceptionState&);
-};
-
-{{exported}}v8::Local<v8::Value> toV8(const {{container.cpp_class}}&, v8::Local<v8::Object>, v8::Isolate*);
-
-template <class CallbackInfo>
-inline void v8SetReturnValue(const CallbackInfo& callbackInfo, {{container.cpp_class}}& impl)
-{
-    v8SetReturnValue(callbackInfo, toV8(impl, callbackInfo.Holder(), callbackInfo.GetIsolate()));
-}
-
-template <>
-struct NativeValueTraits<{{container.cpp_class}}> {
-    {{exported}}static {{container.cpp_class}} nativeValue(v8::Isolate*, v8::Local<v8::Value>, ExceptionState&);
-};
-
-{% endfor %}
-} // namespace blink
-
-// We need to set canInitializeWithMemset=true because HeapVector supports
-// items that can initialize with memset or have a vtable. It is safe to
-// set canInitializeWithMemset=true for a union type object in practice.
-// See https://codereview.chromium.org/1118993002/#msg5 for more details.
-{% for container in containers %}
-WTF_ALLOW_MOVE_AND_INIT_WITH_MEM_FUNCTIONS(blink::{{container.cpp_class}});
-{% endfor %}
-
-#endif // {{macro_guard}}