add back dart:mirrors content, remove dart:isolate, misc. tweaks/updates

ch02.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
 <chapter id="ch02">
   <?dbhtml stop-chunking?>
 
   <title>A Tour of the Dart Language</title>
 
   <para>This chapter shows you how to use each major Dart feature, from
   variables and operators to classes and libraries, with the assumption that
@@ skipping 2389 matching lines @@
 
 p.y = 3;             // Set the value of the instance variable y.
 assert(p.y == 3);    // Get the value of y.
 
 num distance = p.distanceTo(new Point(4,4)); // Invoke distanceTo() on p.</programlisting>
 
     <para>Use the cascade operator (..) when you want to perform a series of
     operations on the members of a single object:</para>
 
     <programlisting format="linespecific" role="keep-together"><remark>lang-dart
-</remark>query('#button')
+</remark>querySelector('#button')
     ..text = 'Click to Confirm'                        // Get an object. Use its
     ..classes.add('important')                         // instance variables
     ..onClick.listen((e) =&gt; window.alert('Confirmed!')); // and methods.</programlisting>
 
     <para>Some classes provide constant constructors. To create a compile-time
     constant using a constant constructor, use <literal
     moreinfo="none">const</literal> instead of <literal
     moreinfo="none">new</literal>:</para>
 
     <programlisting format="linespecific"><remark>lang-dart
@@ skipping 1130 matching lines @@
 
     <para>Modern web browsers, even on mobile platforms, run on multi-core
     CPUs. To take advantage of all those cores, developers traditionally use
     shared-memory threads running concurrently. However, shared-state
     concurrency is error prone and can lead to complicated code.</para>
 
     <para>Instead of threads, all Dart code runs inside of
     <emphasis>isolates</emphasis>. Each isolate has its own memory heap,
     ensuring that no isolate’s state is accessible from any other
     isolate.</para>
-
-    <para>Learn more about isolates in <xref
-    linkend="ch03-dartisolate---concurrency-with-isolates" />.</para>
   </sect1>
 
   <sect1 id="typedefs">
     <title>Typedefs</title>
 
     <para>In Dart, functions are objects, just like strings and numbers are
     objects. A <emphasis>typedef</emphasis>, or <emphasis>function-type
     alias</emphasis>, gives a function type a name that you can use when
     declaring fields and return types. A typedef retains type information when
     a function type is assigned to a variable.</para>
@@ skipping 240 matching lines @@
     language. More features are being implemented<ulink
     url="http://www.dartlang.org/articles/mixins/">,</ulink> but we expect
     that they won’t break existing code. For more information, see the <ulink
     url="http://www.dartlang.org/docs/spec/">Dart Language
     Specification</ulink> and <ulink
     url="http://www.dartlang.org/articles/">articles</ulink> such as <ulink
     url="http://www.dartlang.org/articles/idiomatic-dart/"
     userlevel="">Idiomatic Dart.</ulink></para>
   </sect1>
 </chapter>