Have a Page's MemoryPurgeController be a separate allocation also.

Source/core/page/Page.cpp

Index: Source/core/page/Page.cpp
diff --git a/Source/core/page/Page.cpp b/Source/core/page/Page.cpp
index ce956576bcff1a312e5c542415f2c0e755788b5d..5796f04850dd8ee386ef52849cf3f17358b886ae 100644
--- a/Source/core/page/Page.cpp
+++ b/Source/core/page/Page.cpp
@@ -47,6 +47,7 @@
 #include "core/page/ValidationMessageClient.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
 #include "core/paint/DeprecatedPaintLayer.h"
+#include "platform/MemoryPurgeController.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/plugins/PluginData.h"
 #include "wtf/RefCountedLeakCounter.h"
@@ -161,6 +162,14 @@ ScrollingCoordinator* Page::scrollingCoordinator()
     return m_scrollingCoordinator.get();
 }
 
+MemoryPurgeController& Page::memoryPurgeController()
+{
+    if (!m_memoryPurgeController)
+        m_memoryPurgeController = MemoryPurgeController::create();
+
+    return *m_memoryPurgeController;
+}
+
 String Page::mainThreadScrollingReasonsAsText()
 {
     if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
@@ -557,9 +566,9 @@ DEFINE_TRACE(Page)
     visitor->trace(m_validationMessageClient);
     visitor->trace(m_multisamplingChangedObservers);
     visitor->trace(m_frameHost);
+    visitor->trace(m_memoryPurgeController);
     HeapSupplementable<Page>::trace(visitor);
 #endif
-    visitor->trace(m_memoryPurgeController);
     PageLifecycleNotifier::trace(visitor);
 }