Let store buffer start out small for a 1Mbyte saving in boot

src/store-buffer.h

Index: src/store-buffer.h
===================================================================
--- src/store-buffer.h	(revision 10131)
+++ src/store-buffer.h	(working copy)
@@ -85,6 +85,7 @@
   static const int kStoreBufferSize = kStoreBufferOverflowBit;
   static const int kStoreBufferLength = kStoreBufferSize / sizeof(Address);
   static const int kOldStoreBufferLength = kStoreBufferLength * 16;
+  static const int kInitialOldStoreBufferLength = kOldStoreBufferLength >> 9;
   static const int kHashMapLengthLog2 = 12;
   static const int kHashMapLength = 1 << kHashMapLengthLog2;
 
@@ -109,7 +110,7 @@
   // been promoted.  Rebuilds the store buffer completely if it overflowed.
   void SortUniq();
 
-  void HandleFullness();
+  void EnsureSpace(intptr_t space_needed);
   void Verify();
 
   bool PrepareForIteration();
@@ -134,6 +135,8 @@
   Address* old_start_;
   Address* old_limit_;
   Address* old_top_;
+  Address* old_reserved_limit_;
+  VirtualMemory* old_virtual_memory_;
 
   bool old_buffer_is_sorted_;
   bool old_buffer_is_filtered_;