Bug 1014338 - Pre: add ThreadUtils.assertNotOnUiThread. r=margaret

mobile/android/base/util/ThreadUtils.java

@@ -120,6 +120,10 @@ public final class ThreadUtils {
         assertOnThread(getUiThread(), AssertBehavior.THROW);
     }
 
+    public static void assertNotOnUiThread() {
+        assertNotOnThread(getUiThread(), AssertBehavior.THROW);
+    }
+
     @RobocopTarget
     public static void assertOnGeckoThread() {
         assertOnThread(sGeckoThread, AssertBehavior.THROW);
@@ -134,11 +138,19 @@ public final class ThreadUtils {
     }
 
     public static void assertOnThread(final Thread expectedThread, AssertBehavior behavior) {
+        assertOnThreadComparison(expectedThread, behavior, true);
+    }
+
+    public static void assertNotOnThread(final Thread expectedThread, AssertBehavior behavior) {
+        assertOnThreadComparison(expectedThread, behavior, false);
+    }
+
+    private static void assertOnThreadComparison(final Thread expectedThread, AssertBehavior behavior, boolean expected) {
         final Thread currentThread = Thread.currentThread();
         final long currentThreadId = currentThread.getId();
         final long expectedThreadId = expectedThread.getId();
 
-        if (currentThreadId == expectedThreadId) {
+        if ((currentThreadId == expectedThreadId) == expected) {
             return;
         }