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

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

Index: base/android/java/src/org/chromium/base/ObserverList.java
diff --git a/base/android/java/src/org/chromium/base/ObserverList.java b/base/android/java/src/org/chromium/base/ObserverList.java
index c9a995e866d7b7df76d6459ecf9982d339cc834d..c2bb902fa42b2105d05542758b9e6b41cc49e495 100644
--- a/base/android/java/src/org/chromium/base/ObserverList.java
+++ b/base/android/java/src/org/chromium/base/ObserverList.java
@@ -66,7 +66,7 @@ public class ObserverList<E> implements Iterable<E> {
         // Structurally modifying the underlying list here. This means we
         // cannot use the underlying list's iterator to iterate over the list.
         boolean result = mObservers.add(obs);
-        assert result == true;
+        assert result;
 
         ++mCount;
         return true;