[tracing] Add trace events filtering predicate for heap profiler

base/trace_event/trace_log.h

Index: base/trace_event/trace_log.h
diff --git a/base/trace_event/trace_log.h b/base/trace_event/trace_log.h
index 8cddf272b26926b57fe7db5e963b5cd5db7994ce..540d7d0bd3e0e06aa910b65cb2850ef08143cc62 100644
--- a/base/trace_event/trace_log.h
+++ b/base/trace_event/trace_log.h
@@ -312,8 +312,11 @@ class BASE_EXPORT TraceLog : public MemoryDumpProvider {
   // Allows deleting our singleton instance.
   static void DeleteForTesting();
 
-  class TraceEventFilter {
+  class BASE_EXPORT TraceEventFilter {
    public:
+    static const char* const kEventWhitelistPredicate;
+    static const char* const kHeapProfilerPredicate;
+
     TraceEventFilter() {}
     virtual ~TraceEventFilter() {}
     virtual bool FilterTraceEvent(const TraceEvent& trace_event) const = 0;