Provide baseline GC version.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index c3958e2396848bc87a603b639aab13b42529c6e6..7cab68dfb58a9bc1f5dd4cb0b292b8b3dcef11e5 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -937,6 +937,7 @@ class MapWord BASE_EMBEDDED {
   inline void ClearOverflow();
 
 
+#ifndef BASELINE_GC
   // Compacting phase of a full compacting collection: the map word of live
   // objects contains an encoding of the original map address along with the
   // forwarding address (represented as an offset from the first live object
@@ -960,6 +961,7 @@ class MapWord BASE_EMBEDDED {
   static inline MapWord FromEncodedAddress(Address address);
 
   inline Address ToEncodedAddress();
+#endif
 
   // Bits used by the marking phase of the garbage collector.
   //
@@ -975,6 +977,7 @@ class MapWord BASE_EMBEDDED {
   static const int kOverflowBit = 1;  // overflow bit
   static const int kOverflowMask = (1 << kOverflowBit);  // overflow mask
 
+#ifndef BASELINE_GC
   // Forwarding pointers and map pointer encoding. On 32 bit all the bits are
   // used.
   // +-----------------+------------------+-----------------+
@@ -1008,6 +1011,7 @@ class MapWord BASE_EMBEDDED {
       ((1 << kForwardingOffsetShift) - 1) & ~kMapPageIndexMask;
   static const uintptr_t kForwardingOffsetMask =
       ~(kMapPageIndexMask | kMapPageOffsetMask);
+#endif
 
  private:
   // HeapObject calls the private constructor and directly reads the value.