Alter/use GarbageCollectionTestUtils to deflake unit tests

Bug: 1067622
Change-Id: I1fddfec245cf267100f56756bc9fd38ddacb87ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2137868
Commit-Queue: Brandon Wylie <wylieb@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757127}

base/android/junit/src/org/chromium/base/DiscardableReferencePoolTest.java

@@ -43,11 +43,9 @@ public class DiscardableReferencePoolTest {
         Assert.assertNull(discardableReference.get());
 
         // The object is not (strongly) reachable anymore, so the weak reference may or may not be
-        // null (it could be if a GC has happened since the pool was drained).
-        // After an explicit GC call it definitely should be null.
-        Runtime.getRuntime().gc();
-
-        Assert.assertNull(weakReference.get());
+        // null (it could be if a GC has happened since the pool was drained). It should be
+        // eligible for garbage collection.
+        Assert.assertTrue(GarbageCollectionTestUtils.canBeGarbageCollected(weakReference));
     }
 
     @Test
@@ -72,11 +70,9 @@ public class DiscardableReferencePoolTest {
         Assert.assertNull(discardableReference.get());
 
         // The object is not (strongly) reachable anymore, so the weak reference may or may not be
-        // null (it could be if a GC has happened since the pool was drained).
-        // After an explicit GC call it definitely should be null.
-        Runtime.getRuntime().gc();
-
-        Assert.assertNull(weakReference.get());
+        // null (it could be if a GC has happened since the pool was drained). It should be
+        // eligible for garbage collection.
+        Assert.assertTrue(GarbageCollectionTestUtils.canBeGarbageCollected(weakReference));
     }
 
     @Test
@@ -101,11 +97,9 @@ public class DiscardableReferencePoolTest {
         Assert.assertNull(discardableReference.get());
 
         // The object is not (strongly) reachable anymore, so the weak reference may or may not be
-        // null (it could be if a GC has happened since the pool was drained).
-        // After an explicit GC call it definitely should be null.
-        Runtime.getRuntime().gc();
-
-        Assert.assertNull(weakReference.get());
+        // null (it could be if a GC has happened since the pool was drained). It should be
+        // eligible for garbage collection.
+        Assert.assertTrue(GarbageCollectionTestUtils.canBeGarbageCollected(weakReference));
     }
 
     /**
@@ -129,10 +123,8 @@ public class DiscardableReferencePoolTest {
         discardableReference = null;
 
         // The object is not (strongly) reachable anymore, so the weak reference may or may not be
-        // null (it could be if a GC has happened since the pool was drained).
-        // After an explicit GC call it definitely should be null.
-        Runtime.getRuntime().gc();
-
-        Assert.assertNull(weakReference.get());
+        // null (it could be if a GC has happened since the pool was drained). It should be
+        // eligible for garbage collection.
+        Assert.assertTrue(GarbageCollectionTestUtils.canBeGarbageCollected(weakReference));
     }
 }

base/test/android/java/src/org/chromium/base/GarbageCollectionTestUtils.java

@@ -4,8 +4,6 @@
 
 package org.chromium.base;
 
-import android.os.Build;
-
 import java.lang.ref.WeakReference;
 
 /**
@@ -17,8 +15,8 @@ public class GarbageCollectionTestUtils {
      * Note that {@link #MAX_GC_ITERATIONS} * {@link #GC_SLEEP_TIME} should not be too large,
      * since there are tests asserting objects NOT garbage collected.
      */
-    private final static int MAX_GC_ITERATIONS = 3;
-    private final static long GC_SLEEP_TIME = 100;
+    private static final int MAX_GC_ITERATIONS = 3;
+    private static final long GC_SLEEP_TIME = 10;
 
     /**
      * Do garbage collection and see if an object is released.
@@ -27,8 +25,8 @@ public class GarbageCollectionTestUtils {
      */
     public static boolean canBeGarbageCollected(WeakReference<?> reference) {
         // Robolectric tests, one iteration is enough.
-        final int iterations = isInRobolectric() ? 1 : MAX_GC_ITERATIONS;
-        final long sleepTime = isInRobolectric() ? 0 : GC_SLEEP_TIME;
+        final int iterations = MAX_GC_ITERATIONS;
+        final long sleepTime = GC_SLEEP_TIME;
         Runtime runtime = Runtime.getRuntime();
         for (int i = 0; i < iterations; i++) {
             runtime.runFinalization();
@@ -45,8 +43,4 @@ public class GarbageCollectionTestUtils {
 
         return reference.get() == null;
     }
-
-    private static boolean isInRobolectric() {
-        return Build.FINGERPRINT.equals("robolectric");
-    }
 }