Put back the reduction of semispace sizes as an isolated change.

The growth policy change is next.
Review URL: http://codereview.chromium.org/173050

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2713 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.cc

@@ -74,11 +74,11 @@ int Heap::semispace_size_  = 512*KB;
 int Heap::old_generation_size_ = 128*MB;
 int Heap::initial_semispace_size_ = 128*KB;
 #elseif defined(V8_TARGET_ARCH_X64)
-int Heap::semispace_size_  = 16*MB;
+int Heap::semispace_size_  = 8*MB;
 int Heap::old_generation_size_ = 1*GB;
 int Heap::initial_semispace_size_ = 1*MB;
 #else
-int Heap::semispace_size_  = 8*MB;
+int Heap::semispace_size_  = 4*MB;
 int Heap::old_generation_size_ = 512*MB;
 int Heap::initial_semispace_size_ = 512*KB;
 #endif