Improve the casing of Stackmap and Stacktrace.

runtime/vm/snapshot.cc

Index: runtime/vm/snapshot.cc
diff --git a/runtime/vm/snapshot.cc b/runtime/vm/snapshot.cc
index b7a1b83c5e8e6aa1d04e29462b6fd0e7ea240616..d1e07e6571b1d3548229f9e4500eb0d95732c899 100644
--- a/runtime/vm/snapshot.cc
+++ b/runtime/vm/snapshot.cc
@@ -370,7 +370,7 @@ void SnapshotReader::SetReadException(const char* msg) {
   const Library& library = Library::Handle(zone(), Library::CoreLibrary());
   result = DartLibraryCalls::InstanceCreate(library, Symbols::ArgumentError(),
                                             Symbols::Dot(), args);
-  const Stacktrace& stacktrace = Stacktrace::Handle(zone());
+  const StackTrace& stacktrace = StackTrace::Handle(zone());
   const UnhandledException& error = UnhandledException::Handle(
       zone(), UnhandledException::New(Instance::Cast(result), stacktrace));
   thread()->long_jump_base()->Jump(1, error);