[Checkstyle] Enable left and right curly checks in Java.

BUG=318404,320774
R=newt@chromium.org

Review URL: https://codereview.chromium.org/582303002

Cr-Commit-Position: refs/heads/master@{#295639}

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

@@ -87,10 +87,10 @@
       <property name="max" value="100"/>
     </module>
     <module name="LeftCurly">
-      <property name="severity" value="warning"/>
+      <property name="severity" value="error"/>
     </module>
     <module name="RightCurly">
-      <property name="severity" value="warning"/>
+      <property name="severity" value="error"/>
     </module>
     <module name="NeedBraces">
       <property name="severity" value="warning"/>