Oilpan: have Navigator plugin objects on the heap by default.

Source/modules/plugins/DOMMimeTypeArray.cpp

Index: Source/modules/plugins/DOMMimeTypeArray.cpp
diff --git a/Source/modules/plugins/DOMMimeTypeArray.cpp b/Source/modules/plugins/DOMMimeTypeArray.cpp
index 7e367a093de9aac7cd2960c35ad71b94b020c82a..d5d0121d8af598c58a23f9115eaaf773f85fd4b9 100644
--- a/Source/modules/plugins/DOMMimeTypeArray.cpp
+++ b/Source/modules/plugins/DOMMimeTypeArray.cpp
@@ -46,7 +46,7 @@ unsigned DOMMimeTypeArray::length() const
     return data->mimes().size();
 }
 
-PassRefPtrWillBeRawPtr<DOMMimeType> DOMMimeTypeArray::item(unsigned index)
+DOMMimeType* DOMMimeTypeArray::item(unsigned index)
 {
     PluginData* data = getPluginData();
     if (!data)
@@ -57,7 +57,7 @@ PassRefPtrWillBeRawPtr<DOMMimeType> DOMMimeTypeArray::item(unsigned index)
     return DOMMimeType::create(data, m_frame, index);
 }
 
-PassRefPtrWillBeRawPtr<DOMMimeType> DOMMimeTypeArray::namedItem(const AtomicString& propertyName)
+DOMMimeType* DOMMimeTypeArray::namedItem(const AtomicString& propertyName)
 {
     PluginData* data = getPluginData();
     if (!data)