ObserverList.removeObserver() should not return true when null is being removed.

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 87e5e644e11bf8f8e82d93051b18ef92191810b1..012f4755a00e8b12ea3f1443b0506a3d3100c70f 100644
--- a/base/android/java/src/org/chromium/base/ObserverList.java
+++ b/base/android/java/src/org/chromium/base/ObserverList.java
@@ -73,10 +73,14 @@ public class ObserverList<E> implements Iterable<E> {
      * @return true if an element was removed as a result of this call.
      */
     public boolean removeObserver(E obs) {
-        int index = mObservers.indexOf(obs);
+        if (obs == null) {
+            return false;
+        }
 
-        if (index == -1)
+        int index = mObservers.indexOf(obs);
+        if (index == -1) {
             return false;
+        }
 
         if (mIterationDepth == 0) {
             // No one is iterating over the list.