Implement rewind: drop one or more frames from the debugger.

runtime/vm/stub_code_dbc.cc

Index: runtime/vm/stub_code_dbc.cc
diff --git a/runtime/vm/stub_code_dbc.cc b/runtime/vm/stub_code_dbc.cc
index da24e19b745f6f52b295f16ef665111abee979a9..ef4118222cf63b7b2f550aa8d57011dbd022f8a0 100644
--- a/runtime/vm/stub_code_dbc.cc
+++ b/runtime/vm/stub_code_dbc.cc
@@ -47,6 +47,12 @@ void StubCode::GenerateRunExceptionHandlerStub(Assembler* assembler) {
 }
 
 
+// Not executed, but used as a sentinel in Simulator::JumpToFrame.
+void StubCode::GenerateDeoptForRewindStub(Assembler* assembler) {
+  __ Trap();
+}
+
+
 // TODO(vegorov) Don't generate this stub.
 void StubCode::GenerateFixCallersTargetStub(Assembler* assembler) {
   __ Trap();