Oilpan: fix platform unit tests after r188630.

Source/platform/LifecycleContextTest.cpp

 /*
  * Copyright (C) 2013 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 70 matching lines @@
     }
 
     bool m_contextDestroyedCalled;
 
     void unobserve() { observeContext(0); }
 };
 
 TEST(LifecycleContextTest, shouldObserveContextDestroyed)
 {
     OwnPtrWillBeRawPtr<DummyContext> context = adoptPtrWillBeNoop(new DummyContext());
-    TestingObserver* observer = new TestingObserver(context.get());
+    Persistent<TestingObserver> observer = new TestingObserver(context.get());
 
     EXPECT_EQ(observer->lifecycleContext(), context.get());
     EXPECT_FALSE(observer->m_contextDestroyedCalled);
     context->notifyContextDestroyed();
-    context.clear();
+    context = nullptr;
+    Heap::collectAllGarbage();
     EXPECT_EQ(observer->lifecycleContext(), static_cast<DummyContext*>(0));
     EXPECT_TRUE(observer->m_contextDestroyedCalled);
 }
 
 TEST(LifecycleContextTest, shouldNotObserveContextDestroyedIfUnobserve)
 {
     OwnPtrWillBeRawPtr<DummyContext> context = adoptPtrWillBeNoop(new DummyContext());
-    TestingObserver* observer = new TestingObserver(context.get());
+    Persistent<TestingObserver> observer = new TestingObserver(context.get());
     observer->unobserve();
     context->notifyContextDestroyed();
-    context.clear();
+    context = nullptr;
+    Heap::collectAllGarbage();
     EXPECT_EQ(observer->lifecycleContext(), static_cast<DummyContext*>(0));
     EXPECT_FALSE(observer->m_contextDestroyedCalled);
 }
 
 }