Move the Widget hierarchy to the Oilpan heap.

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index c9ca40a569f60048688a9fd98dd7e5f6944bcb0d..eb339e3e8f3fcfe08f5aa7b3abb2d16866718dfe 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -490,7 +490,7 @@ void WebViewImpl::handleMouseDown(LocalFrame& mainFrame, const WebMouseEvent& ev
     // If there is a popup open, close it as the user is clicking on the page (outside of the
     // popup). We also save it so we can prevent a click on an element from immediately
     // reopening the same popup.
-    RefPtr<PopupContainer> selectPopup;
+    RefPtrWillBeRawPtr<PopupContainer> selectPopup = nullptr;
     RefPtr<WebPagePopupImpl> pagePopup;
     if (event.button == WebMouseEvent::ButtonLeft) {
         selectPopup = m_selectPopup;
@@ -740,7 +740,7 @@ bool WebViewImpl::handleGestureEvent(const WebGestureEvent& event)
             break;
         }
 
-        RefPtr<PopupContainer> selectPopup;
+        RefPtrWillBeRawPtr<PopupContainer> selectPopup = nullptr;
         selectPopup = m_selectPopup;
         hideSelectPopup();
         ASSERT(!m_selectPopup);
@@ -3260,7 +3260,7 @@ void WebViewImpl::updateMainFrameLayoutSize()
     if (m_shouldAutoResize || !mainFrameImpl())
         return;
 
-    RefPtr<FrameView> view = mainFrameImpl()->frameView();
+    RefPtrWillBeRawPtr<FrameView> view = mainFrameImpl()->frameView();
     if (!view)
         return;