Fix precompile build issue with IsString change.

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index bada55697e0f465b212e51cc6692285ea029a340..977ba55040acdc93904c958016db44714e6dce62 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -433,27 +433,30 @@ class RawObject {
   }
 
 #define DEFINE_IS_CID(clazz)                                                   \
-  bool Is##clazz() { return ((GetClassId() == k##clazz##Cid)); }
+  bool Is##clazz() const { return ((GetClassId() == k##clazz##Cid)); }
 CLASS_LIST(DEFINE_IS_CID)
 #undef DEFINE_IS_CID
 
 #define DEFINE_IS_CID(clazz)                                                   \
-  bool IsTypedData##clazz() {                                                  \
+  bool IsTypedData##clazz() const {                                            \
     return ((GetClassId() == kTypedData##clazz##Cid));                         \
   }                                                                            \
-  bool IsTypedDataView##clazz() {                                              \
-    return ((GetClassId() == kTypedDataView##clazz##Cid));                     \
+  bool IsTypedDataView##clazz() const {                                        \

[rmacnak, 2016/05/05 18:15:15]

IsTypedData##clazz##View then?

+    return ((GetClassId() == kTypedData##clazz##ViewCid));                     \
   }                                                                            \
-  bool IsExternalTypedData##clazz() {                                          \
+  bool IsExternalTypedData##clazz() const {                                    \
     return ((GetClassId() == kExternalTypedData##clazz##Cid));                 \
-  }                                                                            \
+  }
 CLASS_LIST_TYPED_DATA(DEFINE_IS_CID)
 #undef DEFINE_IS_CID
 
-  bool IsDartInstance() {
+  bool IsStringInstance() const {
+    return IsStringClassId(GetClassId());
+  }
+  bool IsDartInstance() const {
     return (!IsHeapObject() || (GetClassId() >= kInstanceCid));
   }
-  bool IsFreeListElement() {
+  bool IsFreeListElement() const {
     return ((GetClassId() == kFreeListElement));
   }