Oilpan: Make ActiveParserSession::m_document traceable.

ActiveParserSession, NestingLevelIncrementer, and PumpSession are allocatable
only on stack. We can make m_document Member<> without trace().

BUG=357163

Review URL: https://codereview.chromium.org/313033003

git-svn-id: svn://svn.chromium.org/blink/trunk@175458 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/html/parser/HTMLParserScheduler.h

@@ -38,15 +38,17 @@ class Document;
 class HTMLDocumentParser;
 
 class ActiveParserSession {
+    STACK_ALLOCATED();
 public:
     explicit ActiveParserSession(Document*);
     ~ActiveParserSession();
 
 private:
-    RefPtr<Document> m_document;
+    RefPtrWillBeMember<Document> m_document;
 };
 
 class PumpSession : public NestingLevelIncrementer, public ActiveParserSession {
+    STACK_ALLOCATED();
 public:
     PumpSession(unsigned& nestingLevel, Document*);
     ~PumpSession();

third_party/WebKit/Source/core/html/parser/NestingLevelIncrementer.h

@@ -26,11 +26,13 @@
 #ifndef NestingLevelIncrementer_h
 #define NestingLevelIncrementer_h
 
+#include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
 
 namespace WebCore {
 
 class NestingLevelIncrementer {
+    STACK_ALLOCATED();
     WTF_MAKE_NONCOPYABLE(NestingLevelIncrementer);
 public:
     explicit NestingLevelIncrementer(unsigned& nestingLevel)