[Android] Make ApplicationStatus thread safe

- Make sActivityInfo a ConcurrentHashMap instead of just a HashMap.

BUG=403951

Review URL: https://codereview.chromium.org/479603003

Cr-Commit-Position: refs/heads/master@{#290379}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@290379 0039d316-1c4b-4281-b951-d872f2087c98

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

@@ -12,9 +12,9 @@
 
 import java.lang.ref.WeakReference;
 import java.util.ArrayList;
-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
@@ -51,6 +51,7 @@ public ObserverList<ActivityStateListener> getListeners() {
 
     private static Application sApplication;
 
+    private static Object sCachedApplicationStateLock = new Object();
     private static Integer sCachedApplicationState;
 
     /** Last activity that was shown (or null if none or it was destroyed). */
@@ -63,7 +64,7 @@ public ObserverList<ActivityStateListener> getListeners() {
      * A map of which observers listen to state changes from which {@link Activity}.
      */
     private static final Map<Activity, ActivityInfo> sActivityInfo =
-            new HashMap<Activity, ActivityInfo>();
+            new ConcurrentHashMap<Activity, ActivityInfo>();
 
     /**
      * A list of observers to be notified when any {@link Activity} has a state change.
@@ -187,7 +188,9 @@ private static void onStateChange(Activity activity, int newState) {
         }
 
         // Invalidate the cached application state.
-        sCachedApplicationState = null;
+        synchronized (sCachedApplicationStateLock) {
+            sCachedApplicationState = null;
+        }
 
         ActivityInfo info = sActivityInfo.get(activity);
         info.setStatus(newState);
@@ -235,7 +238,6 @@ public static Activity getLastTrackedFocusedActivity() {
      * @return A {@link List} of all non-destroyed {@link Activity}s.
      */
     public static List<WeakReference<Activity>> getRunningActivities() {
-        ThreadUtils.assertOnUiThread();
         List<WeakReference<Activity>> activities = new ArrayList<WeakReference<Activity>>();
         for (Activity activity : sActivityInfo.keySet()) {
             activities.add(new WeakReference<Activity>(activity));
@@ -302,7 +304,11 @@ public static int getStateForActivity(Activity activity) {
      * @return The state of the application (see {@link ApplicationState}).
      */
     public static int getStateForApplication() {
-        if (sCachedApplicationState == null) sCachedApplicationState = determineApplicationState();
+        synchronized (sCachedApplicationStateLock) {
+            if (sCachedApplicationState == null) {
+                sCachedApplicationState = determineApplicationState();
+            }
+        }
 
         return sCachedApplicationState.intValue();
     }