Encapsulated the AST ID recording a bit, this time for MIPS.

src/mips/assembler-mips.cc

Index: src/mips/assembler-mips.cc
===================================================================
--- src/mips/assembler-mips.cc	(revision 8670)
+++ src/mips/assembler-mips.cc	(working copy)
@@ -285,7 +285,7 @@
   unbound_labels_count_ = 0;
   block_buffer_growth_ = false;
 
-  ast_id_for_reloc_info_ = kNoASTId;
+  ClearRecordedAstId();
 }
 
 
@@ -1947,9 +1947,8 @@
     }
     ASSERT(buffer_space() >= kMaxRelocSize);  // Too late to grow buffer here.
     if (rmode == RelocInfo::CODE_TARGET_WITH_ID) {
-      ASSERT(ast_id_for_reloc_info_ != kNoASTId);
-      RelocInfo reloc_info_with_ast_id(pc_, rmode, ast_id_for_reloc_info_);
-      ast_id_for_reloc_info_ = kNoASTId;
+      RelocInfo reloc_info_with_ast_id(pc_, rmode, RecordedAstId());
+      ClearRecordedAstId();
       reloc_info_writer.Write(&reloc_info_with_ast_id);
     } else {
       reloc_info_writer.Write(&rinfo);