[Checkstyle] Enable boolean simplification and fix up some issues.

tools/android/checkstyle/chromium-style-5.0.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.3//EN" "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
 
 <!--
   See installation instructions: https://sites.google.com/a/chromium.org/dev/checkstyle
 -->
 <module name="Checker">
   <property name="severity" value="warning"/>
   <property name="charset" value="UTF-8"/>
   <module name="TreeWalker">
@@ skipping 23 matching lines @@
       <property name="scope" value="public"/>
       <property name="allowMissingParamTags" value="true"/>
       <property name="allowMissingPropertyJavadoc" value="true"/>
       <property name="allowMissingReturnTag" value="true"/>
       <property name="allowMissingThrowsTags" value="true"/>
     </module>
     <module name="PackageName">
       <property name="severity" value="error"/>
       <property name="format" value="^[a-z]+(\.[a-z][a-z0-9_]{1,})*$"/>
     </module>
+    <module name="SimplifyBooleanExpression">
+      <property name="severity" value="error"/>
+    </module>
+    <module name="SimplifyBooleanReturn">
+      <property name="severity" value="error"/>
+    </module>
     <module name="TypeName">
       <property name="severity" value="error"/>
     </module>
     <module name="ConstantName">
       <property name="severity" value="error"/>
       <property name="format" value="^([A-Z][A-Z0-9]*(_[A-Z0-9]+)*)|(s[A-Z][a-zA-Z0-9]*)$"/>
       <message key="name.invalidPattern" value="Static final field names must either be all caps (e.g. int HEIGHT_PX) for 'true' constants, or start with s (e.g. AtomicInteger sNextId or Runnable sSuspendTask) for fields with mutable state or that don't 'feel' like constants."/>
     </module>
     <!-- Non-public, non-static field names start with m. -->
     <module name="MemberName">
@@ skipping 68 matching lines @@
     </module>
     <module name="NoWhitespaceAfter">
       <property name="severity" value="error"/>
       <property name="tokens" value="BNOT, DEC, DOT, INC, LNOT, UNARY_MINUS, UNARY_PLUS"/>
     </module>
     <module name="NoWhitespaceBefore">
       <property name="severity" value="error"/>
       <property name="allowLineBreaks" value="true"/>
       <property name="tokens" value="SEMI, DOT, POST_DEC, POST_INC"/>
     </module>
+    <module name="EmptyStatement">
+      <property name="severity" value="error"/>
+    </module>
     <module name="NoFinalizer">
       <property name="severity" value="warning"/>
     </module>
     <module name="ParenPad">
       <property name="severity" value="warning"/>
     </module>
     <module name="ImportOrder">
       <property name="severity" value="error"/>
       <message key="import.ordering" value="Wrong order for {0} import. Use :JavaImportOrganize (ECLIM) or Ctrl+Shift+O (Eclipse) to sort imports"/>
       <property name="groups" value="android, com, dalvik, gov, junit, libcore, net, org, java, javax"/>
@@ skipping 20 matching lines @@
   <module name="RegexpSingleline">
     <property name="severity" value="error"/>
     <property name="format" value="[ \t]+$"/>
     <property name="message" value="Trailing whitespace"/>
     </module>
   <module name="RegexpHeader">
     <property name="severity" value="error"/>
     <property name="header" value="^// Copyright 20\d\d The Chromium Authors. All rights reserved.$\n^// Use of this source code is governed by a BSD-style license that can be$\n^// found in the LICENSE file.$"/>
   </module>
 </module>