Improve CleanupReference & add test

content/public/android/javatests/src/org/chromium/content/common/CleanupReferenceTest.java

Index: content/public/android/javatests/src/org/chromium/content/common/CleanupReferenceTest.java
diff --git a/content/public/android/javatests/src/org/chromium/content/common/CleanupReferenceTest.java b/content/public/android/javatests/src/org/chromium/content/common/CleanupReferenceTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..a887ffb051ffae7eabd0c9bb5376b584a8a9072d
--- /dev/null
+++ b/content/public/android/javatests/src/org/chromium/content/common/CleanupReferenceTest.java
@@ -0,0 +1,93 @@
+// 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.content.common;
+
+import android.test.InstrumentationTestCase;
+import android.test.suitebuilder.annotation.SmallTest;
+
+import org.chromium.base.test.util.Feature;
+import org.chromium.content.browser.test.util.Criteria;
+import org.chromium.content.browser.test.util.CriteriaHelper;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class CleanupReferenceTest extends InstrumentationTestCase {
+
+    private static AtomicInteger sObjectCount = new AtomicInteger();
+
+    private static class ReferredObject {
+
+        private CleanupReference mRef;
+
+        // Remember: this MUST be a static class, to avoid an implicit ref back to the
+        // owning ReferredObject instance which would defeat GC of that object.
+        private static class DestroyRunnable implements Runnable {
+            @Override
+            public void run() {
+                sObjectCount.decrementAndGet();
+            }
+        };
+
+        public ReferredObject() {
+            sObjectCount.incrementAndGet();
+            mRef = new CleanupReference(this, new DestroyRunnable());
+        }
+    }
+
+    @Override
+    public void setUp() throws Exception {
+        super.setUp();
+        sObjectCount.set(0);
+    }
+
+    private void collectGarbage() {
+        // While this is only a 'hint' to the VM, it's generally effective and sufficient on
+        // dalvik. If this changes in future, maybe try allocating a few gargantuan objects
+        // too, to force the GC to work.
+        System.gc();
+    }
+
+    @SmallTest
+    @Feature({"AndroidWebView"})
+    public void testCreateSingle() throws Throwable {
+        assertEquals(0, sObjectCount.get());
+
+        ReferredObject instance = new ReferredObject();
+        assertEquals(1, sObjectCount.get());
+
+        instance = null;
+        collectGarbage();
+        assertTrue(CriteriaHelper.pollForCriteria(new Criteria() {
+            @Override
+            public boolean isSatisfied() {
+                return sObjectCount.get() == 0;
+            }
+        }));
+    }
+
+    @SmallTest
+    @Feature({"AndroidWebView"})
+    public void testCreateMany() throws Throwable {
+        assertEquals(0, sObjectCount.get());
+
+        final int INSTANCE_COUNT = 20;
+        ReferredObject[] instances = new ReferredObject[INSTANCE_COUNT];
+
+        for (int i = 0; i < INSTANCE_COUNT; ++i) {
+            instances[i] = new ReferredObject();
+            assertEquals(i + 1, sObjectCount.get());
+        }
+
+        instances = null;
+        collectGarbage();
+        assertTrue(CriteriaHelper.pollForCriteria(new Criteria() {
+            @Override
+            public boolean isSatisfied() {
+                return sObjectCount.get() == 0;
+            }
+        }));
+    }
+
+}