Remove PSS::ShowLoginDialog() and obsolete IDC_SYNC_BOOKMARKS.

chrome/app/nibs/MainMenu.xib

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 <archive type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="7.10">
         <data>
                 <int key="IBDocument.SystemTarget">1050</int>
                 <string key="IBDocument.SystemVersion">10K549</string>
                 <string key="IBDocument.InterfaceBuilderVersion">851</string>
                 <string key="IBDocument.AppKitVersion">1038.36</string>
                 <string key="IBDocument.HIToolboxVersion">461.00</string>
                 <object class="NSMutableDictionary" key="IBDocument.PluginVersions">
                         <string key="NS.key.0">com.apple.InterfaceBuilder.CocoaPlugin</string>
@@ skipping 86 matching lines @@
                                                                 </object>
                                                                 <object class="NSMenuItem" id="214319129">
                                                                         <reference key="NSMenu" ref="110575045"/>
                                                                         <bool key="NSIsDisabled">YES</bool>
                                                                         <bool key="NSIsHidden">YES</bool>
                                                                         <string key="NSTitle">^IDS_SYNC_MENU_PRE_SYNCED_LABEL$IDS_PRODUCT_NAME</string>
                                                                         <string key="NSKeyEquiv"/>
                                                                         <int key="NSMnemonicLoc">2147483647</int>
                                                                         <reference key="NSOnImage" ref="353210768"/>
                                                                         <reference key="NSMixedImage" ref="549394948"/>
-                                                                        <int key="NSTag">41108</int>
+                                                                        <int key="NSTag">40030</int>
                                                                 </object>
                                                                 <object class="NSMenuItem" id="52470633">
                                                                         <reference key="NSMenu" ref="110575045"/>
                                                                         <string key="NSTitle">^IDS_CLEAR_BROWSING_DATA</string>
                                                                         <string type="base64-UTF8" key="NSKeyEquiv">CA</string>
                                                                         <int key="NSKeyEquivModMask">1179648</int>
                                                                         <int key="NSMnemonicLoc">2147483647</int>
                                                                         <reference key="NSOnImage" ref="353210768"/>
                                                                         <reference key="NSMixedImage" ref="549394948"/>
                                                                         <int key="NSTag">40013</int>
@@ skipping 4153 matching lines @@
                                 <string>NSMenuMixedState</string>
                         </object>
                         <object class="NSMutableArray" key="dict.values">
                                 <bool key="EncodedWithXMLCoder">YES</bool>
                                 <string>{9, 8}</string>
                                 <string>{7, 2}</string>
                         </object>
                 </object>
         </data>
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