Use clustered serialization for full snapshots.

runtime/lib/stacktrace.cc

Index: runtime/lib/stacktrace.cc
diff --git a/runtime/lib/stacktrace.cc b/runtime/lib/stacktrace.cc
index 9d9a3075d0df62820dc5eee8fb3c2336c647c738..a63d66dd805afdc02fbf18e3d71d3a6fdfaf569f 100644
--- a/runtime/lib/stacktrace.cc
+++ b/runtime/lib/stacktrace.cc
@@ -61,6 +61,16 @@ void _printCurrentStacktrace() {
   OS::PrintErr("=== Current Trace:\n%s===\n", stacktrace.ToCString());
 }
 
+// Like _printCurrentStacktrace, but works in a NoSafepointScope.
+void _printCurrentStacktraceNoSafepoint() {
+  StackFrameIterator frames(StackFrameIterator::kDontValidateFrames);
+  StackFrame* frame = frames.NextFrame();
+  while (frame != NULL) {
+    OS::Print("%s\n", frame->ToCString());
+    frame = frames.NextFrame();
+  }
+}

[siva, 2016/06/30 00:06:07]

Do we need the other version, why not make your version
_printCurrentStacktrace() and get rid of the existing version.

[rmacnak, 2016/06/30 01:39:21]

The existing version is often preferable when it works because you get line
numbers. The new version is helpful for lower-level bugs.

+
 DEFINE_NATIVE_ENTRY(StackTrace_current, 0) {
   const Stacktrace& stacktrace = GetCurrentStacktrace(1);
   return stacktrace.raw();