Always use the observer's index in ObserverList.removeObserver().

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 d10dc6a0ce1d0fa0e859bc47632b435a22cfa533..87e5e644e11bf8f8e82d93051b18ef92191810b1 100644
--- a/base/android/java/src/org/chromium/base/ObserverList.java
+++ b/base/android/java/src/org/chromium/base/ObserverList.java
@@ -80,7 +80,7 @@ public class ObserverList<E> implements Iterable<E> {
 
         if (mIterationDepth == 0) {
             // No one is iterating over the list.
-            mObservers.remove(obs);
+            mObservers.remove(index);
         } else {
             mObservers.set(index, null);
         }