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

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

Index: tools/android/checkstyle/chromium-style-5.0.xml
diff --git a/tools/android/checkstyle/chromium-style-5.0.xml b/tools/android/checkstyle/chromium-style-5.0.xml
index 8bc7d51369fdbde6b130b8c87a10454eb62b30e5..938a7c8ead92f75aba3117e4407a5b5bfd4f50c7 100644
--- a/tools/android/checkstyle/chromium-style-5.0.xml
+++ b/tools/android/checkstyle/chromium-style-5.0.xml
@@ -41,6 +41,12 @@
       <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>
@@ -129,6 +135,9 @@
       <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>