Support merged Dart-JS callstacks

Source/bindings/v8/V8PerIsolateData.h

Index: Source/bindings/v8/V8PerIsolateData.h
diff --git a/Source/bindings/v8/V8PerIsolateData.h b/Source/bindings/v8/V8PerIsolateData.h
index c36a87d910c758af4b6e936b0165e6b7dfd7e3f8..94ce9d6aee0ab4b87a0e3ef24d6110d0e16180fa 100644
--- a/Source/bindings/v8/V8PerIsolateData.h
+++ b/Source/bindings/v8/V8PerIsolateData.h
@@ -26,6 +26,7 @@
 #ifndef V8PerIsolateData_h
 #define V8PerIsolateData_h
 
+#include "bindings/common/StackTrace.h"
 #include "bindings/v8/ScopedPersistent.h"
 #include "bindings/v8/V8ScriptState.h"
 #include "bindings/v8/V8HiddenValue.h"
@@ -72,6 +73,7 @@ public:
     int recursionLevel() const { return m_recursionLevel; }
     int incrementRecursionLevel() { return ++m_recursionLevel; }
     int decrementRecursionLevel() { return --m_recursionLevel; }
+    StackTraceTimestampTracker* stackTraceTimestampTracker() { return &m_stackTraceTimestampTracker; }
 
     bool performingMicrotaskCheckpoint() const { return m_performingMicrotaskCheckpoint; }
     void setPerformingMicrotaskCheckpoint(bool performingMicrotaskCheckpoint) { m_performingMicrotaskCheckpoint = performingMicrotaskCheckpoint; }
@@ -122,6 +124,7 @@ private:
     friend class ConstructorMode;
 
     int m_recursionLevel;
+    StackTraceTimestampTracker m_stackTraceTimestampTracker;
 
 #ifndef NDEBUG
     int m_internalScriptRecursionLevel;