diff --git a/content/treestyletab/boxObject.js b/content/treestyletab/boxObject.js
index e6e8d018..135a0043 100644
--- a/content/treestyletab/boxObject.js
+++ b/content/treestyletab/boxObject.js
@@ -18,45 +18,6 @@
 
 	var Ci = Components.interfaces;
 
-	var getFrameOwnerFromFrame = function(aFrame) {
-		var parentItem = aFrame
-				.QueryInterface(Ci.nsIInterfaceRequestor)
-				.getInterface(Ci.nsIWebNavigation)
-				.QueryInterface(Ci.nsIDocShell)
-				.QueryInterface(Ci.nsIDocShellTreeNode)
-				.QueryInterface(Ci.nsIDocShellTreeItem)
-				.parent;
-		var isChrome = parentItem.itemType == parentItem.typeChrome;
-		var parentDocument = parentItem
-				.QueryInterface(Ci.nsIWebNavigation)
-				.document;
-		var nodes = parentDocument.evaluate(
-				'/descendant::*[contains(" frame FRAME iframe IFRAME browser tabbrowser ", concat(" ", local-name(), " "))]',
-				parentDocument,
-				null,
-				XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
-				null
-			);
-		for (let i = 0, maxi = nodes.snapshotLength; i < maxi; i++)
-		{
-			let owner = nodes.snapshotItem(i);
-			if (isChrome && owner.wrappedJSObject) owner = owner.wrappedJSObject;
-			if (owner.localName == 'tabbrowser') {
-				let tabs = owner.mTabContainer.childNodes;
-				for (let i = 0, maxi = tabs.length; i < maxi; i++)
-				{
-					let browser = tabs[i].linkedBrowser;
-					if (browser.contentWindow == aFrame)
-						return browser;
-				}
-			}
-			else if (owner.contentWindow == aFrame) {
-				return owner;
-			}
-		}
-		return null;
-	};
-
 	window['piro.sakura.ne.jp'].boxObject = {
 		revision : currentRevision,
 
@@ -65,6 +26,11 @@
 			if ('getBoxObjectFor' in aNode.ownerDocument)
 				return aNode.ownerDocument.getBoxObjectFor(aNode);
 
+			return this.getBoxObjectFromClientRectFor(aNode);
+		},
+
+		getBoxObjectFromClientRectFor : function(aNode)
+		{
 			var box = {
 					x       : 0,
 					y       : 0,
@@ -87,7 +53,7 @@
 				while (true)
 				{
 					frame = owner.ownerDocument.defaultView;
-					owner = getFrameOwnerFromFrame(frame);
+					owner = this._getFrameOwnerFromFrame(frame);
 					if (!owner) {
 						box.screenX += frame.screenX;
 						box.screenY += frame.screenY;
@@ -107,6 +73,46 @@
 			catch(e) {
 			}
 			return box;
+		},
+
+		_getFrameOwnerFromFrame : function(aFrame)
+		{
+			var parentItem = aFrame
+					.QueryInterface(Ci.nsIInterfaceRequestor)
+					.getInterface(Ci.nsIWebNavigation)
+					.QueryInterface(Ci.nsIDocShell)
+					.QueryInterface(Ci.nsIDocShellTreeNode)
+					.QueryInterface(Ci.nsIDocShellTreeItem)
+					.parent;
+			var isChrome = parentItem.itemType == parentItem.typeChrome;
+			var parentDocument = parentItem
+					.QueryInterface(Ci.nsIWebNavigation)
+					.document;
+			var nodes = parentDocument.evaluate(
+					'/descendant::*[contains(" frame FRAME iframe IFRAME browser tabbrowser ", concat(" ", local-name(), " "))]',
+					parentDocument,
+					null,
+					XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
+					null
+				);
+			for (let i = 0, maxi = nodes.snapshotLength; i < maxi; i++)
+			{
+				let owner = nodes.snapshotItem(i);
+				if (isChrome && owner.wrappedJSObject) owner = owner.wrappedJSObject;
+				if (owner.localName == 'tabbrowser') {
+					let tabs = owner.mTabContainer.childNodes;
+					for (let i = 0, maxi = tabs.length; i < maxi; i++)
+					{
+						let browser = tabs[i].linkedBrowser;
+						if (browser.contentWindow == aFrame)
+							return browser;
+					}
+				}
+				else if (owner.contentWindow == aFrame) {
+					return owner;
+				}
+			}
+			return null;
 		}
 
 	};