Plumb whether or not a frame is in shadow DOM to the embedder.

Source/web/FrameLoaderClientImpl.cpp

Index: Source/web/FrameLoaderClientImpl.cpp
diff --git a/Source/web/FrameLoaderClientImpl.cpp b/Source/web/FrameLoaderClientImpl.cpp
index 802c78b23d51525b29d5d6f8cbe42ed0f3b473a3..a73a83a8cd1b669d99366c5c9269cd5f3b2c793c 100644
--- a/Source/web/FrameLoaderClientImpl.cpp
+++ b/Source/web/FrameLoaderClientImpl.cpp
@@ -267,6 +267,11 @@ bool FrameLoaderClientImpl::hasWebView() const
     return m_webFrame->viewImpl();
 }
 
+bool FrameLoaderClientImpl::inShadowTree() const
+{
+    return m_webFrame->inShadowTree();
+}
+
 Frame* FrameLoaderClientImpl::opener() const
 {
     return toCoreFrame(m_webFrame->opener());