Use document's contentSize when the HTML element is selected.

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index 3864f1e434b710a86a5094e2334c9fbe2d909701..28d8ea5a7f6d50f18a66661d476a5e1c521c6f7a 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -867,7 +867,10 @@ void WebViewImpl::getSelectionRootBounds(WebRect& bounds) const
                 && toHTMLInputElement(*shadowHost).isText())))
         root = shadowHost;
 
-    IntRect boundingBox = root->pixelSnappedBoundingBox();
+    IntRect boundingBox = isHTMLHtmlElement(root)
+        ? IntRect(IntPoint(0, 0), root->document().frame()->view()->contentsSize())
+        : root->pixelSnappedBoundingBox();
+
     boundingBox = root->document().frame()->view()->contentsToWindow(boundingBox);
     boundingBox.scale(pageScaleFactor());
     bounds = boundingBox;