Add instruction tags to saved ICData (debug mode only).

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index 5b5ac04d502a2b9096de257f0f69903968046088..231e9eff503f63daa550b4697714bcdce4304410 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -89,7 +89,15 @@ const ICData* Instruction::GetICData(
   // computations added in the optimizing compiler.
   ASSERT(deopt_id_ != Thread::kNoDeoptId);
   if (deopt_id_ < ic_data_array.length()) {
-    return ic_data_array[deopt_id_];
+    const ICData* result = ic_data_array[deopt_id_];
+#if defined(TAG_IC_DATA)
+    if (result->tag() == -1) {
+      result->set_tag(tag());
+    } else if (result->tag() != tag()) {
+      FATAL("ICData tag mismatch");
+    }
+#endif
+    return result;
   }
   return NULL;
 }