Don't use one-bit bit fields for enums -- they misbehave and are inefficient in VC++

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index d6acd1efcaf10ae7a7fa64026710aeeab2451ad2..18ce16b8e38799705f0f4ddb5336e05e1842c23c 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -6806,8 +6806,9 @@ class HLoadKeyedGeneric FINAL : public HTemplateInstruction<3> {
 
 
 // Indicates whether the store is a store to an entry that was previously
-// initialized or not.
-enum StoreFieldOrKeyedMode {
+// initialized or not. Force this enum into an unsigned char to make it
+// take less space.
+enum StoreFieldOrKeyedMode : unsigned char {
   // The entry could be either previously initialized or not.
   INITIALIZING_STORE,
   // At the time of this store it is guaranteed that the entry is already
@@ -6956,8 +6957,8 @@ class HStoreNamedField FINAL : public HTemplateInstruction<3> {
 
   HObjectAccess access_;
   HValue* dominator_;
-  bool has_transition_ : 1;
-  StoreFieldOrKeyedMode store_mode_ : 1;
+  bool has_transition_;
+  StoreFieldOrKeyedMode store_mode_;
 };
 
 
@@ -7170,9 +7171,9 @@ class HStoreKeyed FINAL
 
   ElementsKind elements_kind_;
   uint32_t base_offset_;
-  bool is_dehoisted_ : 1;
-  bool is_uninitialized_ : 1;
-  StoreFieldOrKeyedMode store_mode_: 1;
+  bool is_dehoisted_;
+  bool is_uninitialized_;
+  StoreFieldOrKeyedMode store_mode_;
   HValue* dominator_;
 };