[turbofan] Add DebugBreak machine operator and support

src/compiler/code-assembler.h

Index: src/compiler/code-assembler.h
diff --git a/src/compiler/code-assembler.h b/src/compiler/code-assembler.h
index d32093496bd33f813e56aaecd04e3133f21340ce..24ea44c08fe8d1a8ae75af9898119719751ac71c 100644
--- a/src/compiler/code-assembler.h
+++ b/src/compiler/code-assembler.h
@@ -209,6 +209,8 @@ class CodeAssembler {
   void GotoUnless(Node* condition, Label* false_label);
   void Branch(Node* condition, Label* true_label, Label* false_label);
 
+  void DebugBreak();

[Michael Starzinger, 2016/05/19 08:53:23]

nit: Can we move this up or down a few lines? Right now it sits right in between
the control flow operators (i.e. between Branch and Switch). How about line 205
instead?

[danno, 2016/05/19 09:05:04]

Done.

+
   void Switch(Node* index, Label* default_label, int32_t* case_values,
               Label** case_labels, size_t case_count);