Track async causal stack traces

runtime/lib/stacktrace.h

Index: runtime/lib/stacktrace.h
diff --git a/runtime/lib/stacktrace.h b/runtime/lib/stacktrace.h
index fe67a9dcd9723ee19b778aba3b86dc901e35a0b0..c4820709211ba104e2eb7c8d57d1c0729a8c52f4 100644
--- a/runtime/lib/stacktrace.h
+++ b/runtime/lib/stacktrace.h
@@ -8,6 +8,7 @@
 namespace dart {
 
 class StackTrace;
+class RawStackTrace;
 
 // Creates a StackTrace object from the current stack.  Skips the
 // first skip_frames Dart frames.
@@ -16,6 +17,9 @@ class StackTrace;
 // assertion failures, etc.
 const StackTrace& GetCurrentStackTrace(int skip_frames);
 
+// Creates a StackTrace object to be attached to an exception.
+RawStackTrace* GetStackTraceForException();
+
 }  // namespace dart
 
 #endif  // RUNTIME_LIB_STACKTRACE_H_