Don't add the catch frame at a rethrow to the stacktrace.

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 18578 matching lines @@
   result.set_code_array(code_array);
   result.set_pc_offset_array(pc_offset_array);
   result.SetCatchStacktrace(Object::empty_array(),
                             Object::empty_array());
   result.set_expand_inlined(true);  // default.
   return result.raw();
 }
 
 
 void Stacktrace::Append(const Array& code_list,
-                        const Array& pc_offset_list) const {
+                        const Array& pc_offset_list,
+                        const intptr_t start_index) const {
+  ASSERT(start_index <= code_list.Length());
+  ASSERT(pc_offset_list.Length() == code_list.Length());
   intptr_t old_length = Length();
-  intptr_t new_length = old_length + pc_offset_list.Length();
-  ASSERT(pc_offset_list.Length() == code_list.Length());
+  intptr_t new_length = old_length + pc_offset_list.Length() - start_index;
+  if (new_length == old_length) {
+    // Nothing to append. Avoid work and an assert that growing arrays always
+    // increases their size.
+    return;
+  }
 
-  // Grow the arrays for function, code and pc_offset triplet to accommodate
-  // the new stack frames.
+  // Grow the arrays for code, pc_offset pairs to accommodate the new stack
+  // frames.
   Array& code_array = Array::Handle(raw_ptr()->code_array_);
   Array& pc_offset_array = Array::Handle(raw_ptr()->pc_offset_array_);
   code_array = Array::Grow(code_array, new_length);
   pc_offset_array = Array::Grow(pc_offset_array, new_length);
   set_code_array(code_array);
   set_pc_offset_array(pc_offset_array);
   // Now append the new function and code list to the existing arrays.
-  intptr_t j = 0;
+  intptr_t j = start_index;
   Object& obj = Object::Handle();
   for (intptr_t i = old_length; i < new_length; i++, j++) {
     obj = code_list.At(j);
     code_array.SetAt(i, obj);
     obj = pc_offset_list.At(j);
     pc_offset_array.SetAt(i, obj);
   }
 }
 
 
@@ skipping 453 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart