DevTools: follow up to r183724, mark all floating components as roots.

Source/devtools/front_end/ui/DOMExtension.js

Index: Source/devtools/front_end/ui/DOMExtension.js
diff --git a/Source/devtools/front_end/ui/DOMExtension.js b/Source/devtools/front_end/ui/DOMExtension.js
index 77b5856ecbe0493f3c3d7b9c488065b36194913f..d862f94212839c823b06dc74b64cd0f377d55f74 100644
--- a/Source/devtools/front_end/ui/DOMExtension.js
+++ b/Source/devtools/front_end/ui/DOMExtension.js
@@ -284,10 +284,17 @@ Element.prototype.measurePreferredSize = function(containerElement)
 {
     containerElement = containerElement || document.body;
     containerElement.appendChild(this);
+    var fakingComponentRoot = false;
+    if (!this.classList.contains("component-root")) {
+        fakingComponentRoot = true;
+        this.classList.add("component-root");
+    }
     this.positionAt(0, 0);
     var result = new Size(this.offsetWidth, this.offsetHeight);
     this.positionAt(undefined, undefined);
     this.remove();
+    if (fakingComponentRoot)
+        this.classList.remove("component-root");
     return result;
 }