Oilpan: Make InspectorInstrumentationCookie stack-allocated

tiny-innerHTML.html allocates a ton of persistent handles in InspectorInstrumentationCookie().
I thought this might be a cause of the regression in tiny-innerHTML.html, but it wasn't.
Thus this is just a cleanup CL.

BUG=340522

Review URL: https://codereview.chromium.org/668453003

git-svn-id: svn://svn.chromium.org/blink/trunk@183940 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/inspector/InspectorInstrumentation.h

@@ -64,6 +64,7 @@ class WorkerInspectorProxy;
 #define FAST_RETURN_IF_NO_FRONTENDS(value) if (!hasFrontends()) return value;
 
 class InspectorInstrumentationCookie {
+    STACK_ALLOCATED();
 public:
     InspectorInstrumentationCookie();
     InspectorInstrumentationCookie(InstrumentingAgents*, int);
@@ -76,7 +77,7 @@ public:
     bool hasMatchingTimelineAgentId(int id) const { return m_timelineAgentId == id; }
 
 private:
-    RefPtrWillBePersistent<InstrumentingAgents> m_instrumentingAgents;
+    RefPtrWillBeMember<InstrumentingAgents> m_instrumentingAgents;
     int m_timelineAgentId;
 };