Android: Replace ConcurrentHashMap usage with Collections.synchronizedMap()

ConcurrentHashMap has a bug on L.
Also adds a checkstyle check to prevent future uses.

Bug: 905903
Change-Id: Ic6afed17b5d7d3c6a150935117fb33e0408955e4
Reviewed-on: https://chromium-review.googlesource.com/c/1407493Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Commit-Queue: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622143}

base/android/java/src/org/chromium/base/ApplicationStatus.java

@@ -21,9 +21,10 @@ import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Proxy;
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.concurrent.ConcurrentHashMap;
 
 /**
  * Provides information about the current activity's status, and a way
@@ -87,7 +88,8 @@ public class ApplicationStatus {
     /**
      * A map of which observers listen to state changes from which {@link Activity}.
      */
-    private static final Map<Activity, ActivityInfo> sActivityInfo = new ConcurrentHashMap<>();
+    private static final Map<Activity, ActivityInfo> sActivityInfo =
+            Collections.synchronizedMap(new HashMap<Activity, ActivityInfo>());
 
     /**
      * A list of observers to be notified when any {@link Activity} has a state change.

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

@@ -126,5 +126,12 @@
       <property name="ignoreComments" value="true"/>
       <property name="message" value="Use ContextUtils.getAppSharedPreferences() instead to access app-wide SharedPreferences."/>
     </module>
+    <module name="RegexpSinglelineJava">
+      <property name="id" value="ConcurrentHashMapCheck"/>
+      <property name="severity" value="error"/>
+      <property name="format" value="ConcurrentHashMap"/>
+      <property name="ignoreComments" value="true"/>
+      <property name="message" value="ConcurrentHashMap has a bug on some Android versions. Use Collections.synchronizedMap() instead (crbug.com/905903)."/>
+    </module>
   </module>
 </module>