[interpreter, debugger] support debug breaks via bytecode array copy

src/runtime/runtime-debug.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/debug/debug.h"
 #include "src/debug/debug-evaluate.h"
 #include "src/debug/debug-frames.h"
 #include "src/debug/debug-scopes.h"
 #include "src/frames-inl.h"
 #include "src/isolate-inl.h"
 #include "src/runtime/runtime.h"
 
 namespace v8 {
 namespace internal {
 
 RUNTIME_FUNCTION(Runtime_DebugBreak) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 0);
   // Get the top-most JavaScript frame.
   JavaScriptFrameIterator it(isolate);
   isolate->debug()->Break(args, it.frame());
-  isolate->debug()->SetAfterBreakTarget(it.frame());
-  return isolate->heap()->undefined_value();
+  return isolate->debug()->SetAfterBreakTarget(it.frame());
 }
 
 
 RUNTIME_FUNCTION(Runtime_HandleDebuggerStatement) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 0);
   if (isolate->debug()->break_points_active()) {
     isolate->debug()->HandleDebugBreak();
   }
   return isolate->heap()->undefined_value();
@@ skipping 1639 matching lines @@
   return Smi::FromInt(isolate->debug()->is_active());
 }
 
 
 RUNTIME_FUNCTION(Runtime_DebugBreakInOptimizedCode) {
   UNIMPLEMENTED();
   return NULL;
 }
 }  // namespace internal
 }  // namespace v8