8058235: identify GCs initiated to update allocation context stats

Reviewed-by: mikael, sjohanss

src/share/vm/gc_interface/gcCause.cpp

@@ -54,6 +54,9 @@ const char* GCCause::to_string(GCCause::Cause cause) {
     case _wb_young_gc:
       return "WhiteBox Initiated Young GC";
 
+    case _update_allocation_context_stats:
+      return "Update Allocation Context Stats";
+
     case _no_gc:
       return "No GC";
 

src/share/vm/gc_interface/gcCause.hpp

@@ -47,6 +47,7 @@ class GCCause : public AllStatic {
     _heap_inspection,
     _heap_dump,
     _wb_young_gc,
+    _update_allocation_context_stats,
 
     /* implementation independent, but reserved for GC use */
     _no_gc,