Fix various errorprone warnings and errors.

base/android/javatests/src/org/chromium/base/ObserverListTest.java

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.base;
 
 import android.test.InstrumentationTestCase;
 import android.test.suitebuilder.annotation.SmallTest;
 
 import org.chromium.base.test.util.Feature;
 
+import java.util.Collection;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 
 /**
  * Tests for (@link ObserverList}.
  */
 public class ObserverListTest extends InstrumentationTestCase {
     interface Observer {
         void observe(int x);
     }
@@ skipping 41 matching lines @@
             mList = list;
             mDoomed = innocent;
         }
 
         @Override
         public void observe(int x) {
             mList.removeObserver(mDoomed);
         }
     }
 
+    @SuppressWarnings("ElementsCountedInLoop")
     private static <T> int getSizeOfIterable(Iterable<T> iterable) {
+        if (iterable instanceof Collection<?>) return ((Collection<?>) iterable).size();
         int num = 0;
         for (T el : iterable) num++;
         return num;
     }
 
     @SmallTest
     @Feature({"Android-AppBase"})
     public void testRemoveWhileIteration() {
         ObserverList<Observer> observerList = new ObserverList<Observer>();
         Foo a = new Foo(1);
@@ skipping 233 matching lines @@
         assertTrue(observerList.isEmpty());
 
         observerList.removeObserver(a);
         observerList.removeObserver(b);
         observerList.removeObserver(null);
         observerList.removeObserver(new Object());
         assertEquals(0, observerList.size());
         assertTrue(observerList.isEmpty());
     }
 }