Allow stepping when paused at isolate start.

runtime/vm/debugger.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/debugger.h"
 
 #include "include/dart_api.h"
 
 #include "vm/code_generator.h"
 #include "vm/code_patcher.h"
@@ skipping 1252 matching lines @@
 
 void Debugger::SetStepOver() {
   resume_action_ = kStepOver;
 }
 
 
 void Debugger::SetStepOut() {
   resume_action_ = kStepOut;
 }
 
+
 RawFunction* Debugger::ResolveFunction(const Library& library,
                                        const String& class_name,
                                        const String& function_name) {
   ASSERT(!library.IsNull());
   ASSERT(!class_name.IsNull());
   ASSERT(!function_name.IsNull());
   if (class_name.Length() == 0) {
     return ResolveLibraryFunction(library, function_name);
   }
   const Class& cls = Class::Handle(library.LookupClass(class_name));
@@ skipping 1032 matching lines @@
   pause_event_ = event;
   obj_cache_ = new RemoteObjectCache(64);
 
   InvokeEventHandler(event);
 
   pause_event_ = NULL;
   obj_cache_ = NULL;    // Zone allocated
 }
 
 
+void Debugger::EnterSingleStepMode() {
+  stepping_fp_ = 0;
+  DeoptimizeWorld();
+  isolate_->set_single_step(true);
+}
+
+
 void Debugger::HandleSteppingRequest(DebuggerStackTrace* stack_trace) {
   stepping_fp_ = 0;
   if (resume_action_ == kSingleStep) {
     // When single stepping, we need to deoptimize because we might be
     // stepping into optimized code.  This happens in particular if
     // the isolate has been interrupted, but can happen in other cases
     // as well.  We need to deoptimize the world in case we are about
     // to call an optimized function.
     DeoptimizeWorld();
     isolate_->set_single_step(true);
@@ skipping 665 matching lines @@
 }
 
 
 void Debugger::RegisterCodeBreakpoint(CodeBreakpoint* bpt) {
   ASSERT(bpt->next() == NULL);
   bpt->set_next(code_breakpoints_);
   code_breakpoints_ = bpt;
 }
 
 }  // namespace dart