Fix the types used in bit fields.

vm/object.h

Index: vm/object.h
===================================================================
--- vm/object.h	(revision 12729)
+++ vm/object.h	(working copy)
@@ -1802,8 +1802,8 @@
     return HasInitializerBit::decode(raw_ptr()->kind_bits_);
   }
   void set_has_initializer(bool has_initializer) const {
-    uword bits = raw_ptr()->kind_bits_;
-    raw_ptr()->kind_bits_ = HasInitializerBit::update(has_initializer, bits);
+    raw_ptr()->kind_bits_ = static_cast<uint8_t>(
+        HasInitializerBit::update(has_initializer, raw_ptr()->kind_bits_));
   }
 
   // Constructs getter and setter names for fields and vice versa.
@@ -1830,16 +1830,13 @@
 
   void set_name(const String& value) const;
   void set_is_static(bool is_static) const {
-    uword bits = raw_ptr()->kind_bits_;
-    raw_ptr()->kind_bits_ = StaticBit::update(is_static, bits);
+    set_kind_bits(StaticBit::update(is_static, raw_ptr()->kind_bits_));
   }
   void set_is_final(bool is_final) const {
-    uword bits = raw_ptr()->kind_bits_;
-    raw_ptr()->kind_bits_ = FinalBit::update(is_final, bits);
+    set_kind_bits(FinalBit::update(is_final, raw_ptr()->kind_bits_));
   }
   void set_is_const(bool value) const {
-    uword bits = raw_ptr()->kind_bits_;
-    raw_ptr()->kind_bits_ = ConstBit::update(value, bits);
+    set_kind_bits(ConstBit::update(value, raw_ptr()->kind_bits_));
   }
   void set_owner(const Class& value) const {
     StorePointer(&raw_ptr()->owner_, value.raw());
@@ -1848,7 +1845,7 @@
     raw_ptr()->token_pos_ = token_pos;
   }
   void set_kind_bits(intptr_t value) const {
-    raw_ptr()->kind_bits_ = value;
+    raw_ptr()->kind_bits_ = static_cast<uint8_t>(value);
   }
   static RawField* New();
 
@@ -1935,7 +1932,7 @@
     intptr_t ReadToken() {
       int64_t value = stream_.ReadUnsigned();
       ASSERT((value >= 0) && (value <= kIntptrMax));
-      return value;
+      return static_cast<intptr_t>(value);
     }
 
     const TokenStream& tokens_;