Make extension shelf resize correctly with the window.

chrome/app/nibs/ExtensionShelf.xib

 <?xml version="1.0" encoding="UTF-8"?>
 <archive type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="7.03">
         <data>
                 <int key="IBDocument.SystemTarget">1050</int>
                 <string key="IBDocument.SystemVersion">9L31a</string>
                 <string key="IBDocument.InterfaceBuilderVersion">677</string>
                 <string key="IBDocument.AppKitVersion">949.54</string>
                 <string key="IBDocument.HIToolboxVersion">353.00</string>
                 <object class="NSMutableArray" key="IBDocument.EditedObjectIDs">
                         <bool key="EncodedWithXMLCoder">YES</bool>
@@ skipping 18 matching lines @@
                                 <string key="NSClassName">ExtensionShelfController</string>
                         </object>
                         <object class="NSCustomObject" id="1003">
                                 <string key="NSClassName">FirstResponder</string>
                         </object>
                         <object class="NSCustomObject" id="1004">
                                 <string key="NSClassName">NSApplication</string>
                         </object>
                         <object class="NSCustomView" id="1005">
                                 <reference key="NSNextResponder"/>
-                                <int key="NSvFlags">268</int>
+                                <int key="NSvFlags">290</int>
                                 <string key="NSFrameSize">{400, 30}</string>
                                 <reference key="NSSuperview"/>
                                 <string key="NSClassName">DownloadShelfView</string>
                         </object>
                 </object>
                 <object class="IBObjectContainer" key="IBDocument.Objects">
                         <object class="NSMutableArray" key="connectionRecords">
                                 <bool key="EncodedWithXMLCoder">YES</bool>
                                 <object class="IBConnectionRecord">
                                         <object class="IBOutletConnection" key="connection">
@@ skipping 135 matching lines @@
                                                 <string key="minorKey">browser/cocoa/tab_strip_model_observer_bridge.h</string>
                                         </object>
                                 </object>
                         </object>
                 </object>
                 <int key="IBDocument.localizationMode">0</int>
                 <string key="IBDocument.LastKnownRelativeProjectPath">../../chrome.xcodeproj</string>
                 <int key="IBDocument.defaultPropertyAccessControl">3</int>
         </data>
 </archive>