bindings: Use Maybe APIs in ScriptPromise

Source/bindings/core/v8/ScriptValue.h

Index: Source/bindings/core/v8/ScriptValue.h
diff --git a/Source/bindings/core/v8/ScriptValue.h b/Source/bindings/core/v8/ScriptValue.h
index 7ad2aecaed7c51507d12e55ea33d1dd2cecd2704..73b366d0cbe4fd67e4690ed372e1f78c823ac2d0 100644
--- a/Source/bindings/core/v8/ScriptValue.h
+++ b/Source/bindings/core/v8/ScriptValue.h
@@ -67,6 +67,14 @@ public:
         ASSERT(isEmpty() || m_scriptState);
     }
 
+    template <typename T>
+    ScriptValue(ScriptState* scriptState, v8::MaybeLocal<T> value)
+        : m_scriptState(scriptState)
+        , m_value(value.IsEmpty() ? nullptr : SharedPersistent<v8::Value>::create(value.ToLocalChecked(), scriptState->isolate()))
+    {
+        ASSERT(isEmpty() || m_scriptState);
+    }
+
     ScriptValue(const ScriptValue& value)
         : m_scriptState(value.m_scriptState)
         , m_value(value.m_value)
@@ -84,6 +92,11 @@ public:
         return m_scriptState ? m_scriptState->isolate() : v8::Isolate::GetCurrent();
     }
 
+    v8::Local<v8::Context> context() const
+    {
+        return m_scriptState ? isolate()->GetCurrentContext() : v8::Local<v8::Context>();

[haraken, 2015/03/25 04:29:59]

This seems wrong. We need to use m_scriptState->context().

Also I don't think it is valid to return an empty context from this method. If
an empty context is returned, the caller side will crash when the empty context
is passed in to a next V8 API.

[bashi, 2015/03/25 04:56:00]

Done.

+    }
+
     ScriptValue& operator=(const ScriptValue& value)
     {
         if (this != &value) {