[ServiceWorker] Add support of FetchEvent's request.body.

Source/modules/serviceworkers/Request.cpp

Index: Source/modules/serviceworkers/Request.cpp
diff --git a/Source/modules/serviceworkers/Request.cpp b/Source/modules/serviceworkers/Request.cpp
index de03495cba400dc27c08d5ee06d73ce8bc4a6eea..849178b745daa0ff62e368fd2e152df5eba2f475 100644
--- a/Source/modules/serviceworkers/Request.cpp
+++ b/Source/modules/serviceworkers/Request.cpp
@@ -213,6 +213,16 @@ String Request::url() const
     return url;
 }
 
+PassRefPtrWillBeRawPtr<FetchBodyStream> Request::body(ExecutionContext* context)
+{
+    if (!m_request->blobDataHandle())
+        return nullptr;
+    if (!m_fetchBodyStream)
+        m_fetchBodyStream = FetchBodyStream::create(context, m_request->blobDataHandle());
+    return m_fetchBodyStream;
+}
+
+
 String Request::referrer() const
 {
     // "The referrer attribute's getter must return the empty string if
@@ -259,6 +269,7 @@ void Request::trace(Visitor* visitor)
 {
     visitor->trace(m_request);
     visitor->trace(m_headers);
+    visitor->trace(m_fetchBodyStream);
 }
 
 } // namespace blink