Add notification (and unit test) for closing prefs window so it can be cleane...

chrome/app/nibs/en.lproj/Preferences.xib

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@@ skipping 2299 matching lines @@
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                                 <object class="IBConnectionRecord">
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                                                 <string key="label">window</string>
                                                 <reference key="source" ref="1001"/>
                                                 <reference key="destination" ref="871378074"/>
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                                         <int key="connectionID">252</int>
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+                                <object class="IBConnectionRecord">
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+                                                <string key="label">delegate</string>
+                                                <reference key="source" ref="871378074"/>
+                                                <reference key="destination" ref="1001"/>
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                                                 <reference key="children" ref="1000"/>
@@ skipping 1452 matching lines @@
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                         <nil key="sourceID"/>
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