[interpreter] Add support for scalable operands.

src/debug/debug.cc

Index: src/debug/debug.cc
diff --git a/src/debug/debug.cc b/src/debug/debug.cc
index b255bb81a1dd80db2b46599382491d05d74a2b99..2efbd87c6ae9761cd8c43c7e1493bf3a40af5441 100644
--- a/src/debug/debug.cc
+++ b/src/debug/debug.cc
@@ -1579,7 +1579,8 @@ Object* Debug::SetAfterBreakTarget(JavaScriptFrame* frame) {
     int bytecode_offset = interpreted_frame->GetBytecodeOffset();
     interpreter::Bytecode bytecode =
         interpreter::Bytecodes::FromByte(bytecode_array->get(bytecode_offset));
-    return isolate_->interpreter()->GetBytecodeHandler(bytecode);
+    return isolate_->interpreter()->GetBytecodeHandler(
+        bytecode, interpreter::OperandScale::kSingle);

[Yang, 2016/03/21 09:36:13]

Is the operand scale guaranteed to be single here?

What we do here is to load the original bytecode from the original bytecode
array to continue execution as if the original bytecode was there. If the
original bytecode had a different operand scale, this would be wrong?

[oth, 2016/03/21 09:52:14]

If the bytecode has a scaling prefix, then the scaling prefix has the debug
break on it. There are special debug versions of the prefix bytecodes
(DEBUG_BREAK_PREFIX_BYTECODE_LIST). Otherwise, it's the usual mechanism.

   } else {
     after_break_target_ = NULL;
     if (!LiveEdit::SetAfterBreakTarget(this)) {