diff --git a/src/runtime/runtime-debug.cc b/src/runtime/runtime-debug.cc
index c29ea9a..ad8375a 100644
--- a/src/runtime/runtime-debug.cc
+++ b/src/runtime/runtime-debug.cc
@@ -5,11 +5,13 @@
 #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/debug/debug.h"
 #include "src/frames-inl.h"
+#include "src/interpreter/bytecodes.h"
+#include "src/interpreter/interpreter.h"
 #include "src/isolate-inl.h"
 #include "src/runtime/runtime.h"
 
@@ -18,11 +20,39 @@
 
 RUNTIME_FUNCTION(Runtime_DebugBreak) {
   SealHandleScope shs(isolate);
-  DCHECK(args.length() == 0);
+  DCHECK(args.length() == 1);
+  CONVERT_ARG_HANDLE_CHECKED(Object, value, 0);
+  isolate->debug()->set_return_value(value);
+
   // Get the top-most JavaScript frame.
   JavaScriptFrameIterator it(isolate);
-  isolate->debug()->Break(args, it.frame());
-  return isolate->debug()->SetAfterBreakTarget(it.frame());
+  isolate->debug()->Break(it.frame());
+
+  isolate->debug()->SetAfterBreakTarget(it.frame());
+  return *isolate->debug()->return_value();
+}
+
+RUNTIME_FUNCTION(Runtime_DebugBreakOnBytecode) {
+  SealHandleScope shs(isolate);
+  DCHECK(args.length() == 1);
+  CONVERT_ARG_HANDLE_CHECKED(Object, value, 0);
+  isolate->debug()->set_return_value(value);
+
+  // Get the top-most JavaScript frame.
+  JavaScriptFrameIterator it(isolate);
+  isolate->debug()->Break(it.frame());
+
+  // Return the handler from the original bytecode array.
+  DCHECK(it.frame()->is_interpreted());
+  InterpretedFrame* interpreted_frame =
+      reinterpret_cast<InterpretedFrame*>(it.frame());
+  SharedFunctionInfo* shared = interpreted_frame->function()->shared();
+  BytecodeArray* bytecode_array = shared->bytecode_array();
+  int bytecode_offset = interpreted_frame->GetBytecodeOffset();
+  interpreter::Bytecode bytecode =
+      interpreter::Bytecodes::FromByte(bytecode_array->get(bytecode_offset));
+  return isolate->interpreter()->GetBytecodeHandler(
+      bytecode, interpreter::OperandScale::kSingle);
 }
 
 
@@ -302,8 +332,8 @@
   if (name->AsArrayIndex(&index)) {
     Handle<FixedArray> details = isolate->factory()->NewFixedArray(2);
     Handle<Object> element_or_char;
-    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, element_or_char,
-                                       Object::GetElement(isolate, obj, index));
+    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+        isolate, element_or_char, JSReceiver::GetElement(isolate, obj, index));
     details->set(0, *element_or_char);
     details->set(1, PropertyDetails::Empty().AsSmi());
     return *isolate->factory()->NewJSArrayWithElements(details);
@@ -418,8 +448,8 @@
   RUNTIME_ASSERT(obj->HasIndexedInterceptor());
   CONVERT_NUMBER_CHECKED(uint32_t, index, Uint32, args[1]);
   Handle<Object> result;
-  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result,
-                                     Object::GetElement(isolate, obj, index));
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, result, JSReceiver::GetElement(isolate, obj, index));
   return *result;
 }
 
@@ -554,7 +584,11 @@
     // Use the value from the stack.
     if (scope_info->LocalIsSynthetic(i)) continue;
     locals->set(local * 2, scope_info->LocalName(i));
-    locals->set(local * 2 + 1, *(frame_inspector.GetExpression(i)));
+    Handle<Object> value = frame_inspector.GetExpression(i);
+    // TODO(yangguo): We convert optimized out values to {undefined} when they
+    // are passed to the debugger. Eventually we should handle them somehow.
+    if (value->IsOptimizedOut()) value = isolate->factory()->undefined_value();
+    locals->set(local * 2 + 1, *value);
     local++;
   }
   if (local < local_count) {
@@ -587,31 +621,7 @@
   // to the frame information.
   Handle<Object> return_value = isolate->factory()->undefined_value();
   if (at_return) {
-    StackFrameIterator it2(isolate);
-    Address internal_frame_sp = NULL;
-    while (!it2.done()) {
-      if (it2.frame()->is_internal()) {
-        internal_frame_sp = it2.frame()->sp();
-      } else {
-        if (it2.frame()->is_java_script()) {
-          if (it2.frame()->id() == it.frame()->id()) {
-            // The internal frame just before the JavaScript frame contains the
-            // value to return on top. A debug break at return will create an
-            // internal frame to store the return value (eax/rax/r0) before
-            // entering the debug break exit frame.
-            if (internal_frame_sp != NULL) {
-              return_value =
-                  Handle<Object>(Memory::Object_at(internal_frame_sp), isolate);
-              break;
-            }
-          }
-        }
-
-        // Indicate that the previous frame was not an internal frame.
-        internal_frame_sp = NULL;
-      }
-      it2.Advance();
-    }
+    return_value = isolate->debug()->return_value();
   }
 
   // Now advance to the arguments adapter frame (if any). It contains all
@@ -740,33 +750,6 @@
 }
 
 
-// Returns the list of step-in positions (text offset) in a function of the
-// stack frame in a range from the current debug break position to the end
-// of the corresponding statement.
-RUNTIME_FUNCTION(Runtime_GetStepInPositions) {
-  HandleScope scope(isolate);
-  DCHECK(args.length() == 2);
-  CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
-  RUNTIME_ASSERT(isolate->debug()->CheckExecutionState(break_id));
-
-  CONVERT_SMI_ARG_CHECKED(wrapped_id, 1);
-
-  // Get the frame where the debugging is performed.
-  StackFrame::Id id = DebugFrameHelper::UnwrapFrameId(wrapped_id);
-  JavaScriptFrameIterator frame_it(isolate, id);
-  RUNTIME_ASSERT(!frame_it.done());
-
-  List<int> positions;
-  isolate->debug()->GetStepinPositions(frame_it.frame(), id, &positions);
-  Factory* factory = isolate->factory();
-  Handle<FixedArray> array = factory->NewFixedArray(positions.length());
-  for (int i = 0; i < positions.length(); ++i) {
-    array->set(i, Smi::FromInt(positions[i]));
-  }
-  return *factory->NewJSArrayWithElements(array, FAST_SMI_ELEMENTS);
-}
-
-
 // Return an array with scope details
 // args[0]: number: break id
 // args[1]: number: frame index
@@ -1652,15 +1635,6 @@
 }
 
 
-RUNTIME_FUNCTION(Runtime_DebugPromiseEvent) {
-  DCHECK(args.length() == 1);
-  HandleScope scope(isolate);
-  CONVERT_ARG_HANDLE_CHECKED(JSObject, data, 0);
-  isolate->debug()->OnPromiseEvent(data);
-  return isolate->heap()->undefined_value();
-}
-
-
 RUNTIME_FUNCTION(Runtime_DebugAsyncTaskEvent) {
   DCHECK(args.length() == 1);
   HandleScope scope(isolate);