[gc] Add runtime timer for gc prologue and epilogue callbacks

src/counters.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COUNTERS_H_
 #define V8_COUNTERS_H_
 
 #include "include/v8.h"
 #include "src/allocation.h"
 #include "src/base/atomic-utils.h"
@@ skipping 690 matching lines @@
   V(CompileCodeLazy)                                \
   V(CompileDeserialize)                             \
   V(CompileEval)                                    \
   V(CompileFullCode)                                \
   V(CompileIgnition)                                \
   V(CompilerDispatcher)                             \
   V(CompileSerialize)                               \
   V(DeoptimizeCode)                                 \
   V(FunctionCallback)                               \
   V(GC)                                             \
+  V(GC_AllAvailableGarbage)                         \
+  V(GCEpilogueCallback)                             \
+  V(GCPrologueCallback)                             \
   V(GenericNamedPropertyDefinerCallback)            \
   V(GenericNamedPropertyDeleterCallback)            \
   V(GenericNamedPropertyDescriptorCallback)         \
   V(GenericNamedPropertyQueryCallback)              \
   V(GenericNamedPropertySetterCallback)             \
   V(IndexedPropertyDefinerCallback)                 \
   V(IndexedPropertyDeleterCallback)                 \
   V(IndexedPropertyDescriptorCallback)              \
   V(IndexedPropertyGetterCallback)                  \
   V(IndexedPropertyQueryCallback)                   \
@@ skipping 609 matching lines @@
   }
 
   RuntimeCallStats* stats_ = nullptr;
   RuntimeCallTimer timer_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COUNTERS_H_