[oilpan]: Fix webkit unit tests for oilpan.

Source/web/tests/WebViewTest.cpp

Index: Source/web/tests/WebViewTest.cpp
diff --git a/Source/web/tests/WebViewTest.cpp b/Source/web/tests/WebViewTest.cpp
index 60a64287b59825d9f426122b721fd0f98052d5b6..43957ea548f6aae5dfcb2526652f7b814810dc8d 100644
--- a/Source/web/tests/WebViewTest.cpp
+++ b/Source/web/tests/WebViewTest.cpp
@@ -1809,7 +1809,7 @@ TEST_F(WebViewTest, DeleteElementWithRegisteredHandler)
     URLTestHelpers::registerMockedURLLoad(toKURL(url), "simple_div.html");
     WebViewImpl* webViewImpl = m_webViewHelper.initializeAndLoad(url, true);
 
-    WebCore::Document* document = webViewImpl->mainFrameImpl()->frame()->document();
+    RefPtrWillBePersistent<WebCore::Document> document = webViewImpl->mainFrameImpl()->frame()->document();
     WebCore::Element* div = document->getElementById("div");
     WebCore::EventHandlerRegistry& registry = document->frameHost()->eventHandlerRegistry();
 
@@ -1818,6 +1818,13 @@ TEST_F(WebViewTest, DeleteElementWithRegisteredHandler)
 
     WebCore::TrackExceptionState exceptionState;
     div->remove(exceptionState);
+#if ENABLE(OILPAN)
+    // For oilpan we have to force a GC to ensure the event handlers have been removed when
+    // checking below. We do a precise GC (collectAllGarbage does not scan the stack)
+    // to ensure the div element dies. This is also why the Document is in a Persistent
+    // since we want that to stay around.
+    Heap::collectAllGarbage();
+#endif
     EXPECT_FALSE(registry.hasEventHandlers(WebCore::EventHandlerRegistry::ScrollEvent));
 }