Fix compilation issue on Win64.

src/spaces.cc

Index: src/spaces.cc
diff --git a/src/spaces.cc b/src/spaces.cc
index de738fba80ab3cef49f0b5978a68d08045e658c3..1fbad551aff63992553b1161e99aaf8fc854a602 100644
--- a/src/spaces.cc
+++ b/src/spaces.cc
@@ -699,7 +699,7 @@ int MemoryAllocator::CodePageGuardStartOffset() {
 
 
 int MemoryAllocator::CodePageGuardSize() {
-  return OS::CommitPageSize();
+  return static_cast<int>(OS::CommitPageSize());
 }
 
 
@@ -713,7 +713,7 @@ int MemoryAllocator::CodePageAreaStartOffset() {
 int MemoryAllocator::CodePageAreaEndOffset() {
   // We are guarding code pages: the last OS page will be protected as
   // non-writable.
-  return Page::kPageSize - OS::CommitPageSize();
+  return Page::kPageSize - static_cast<int>(OS::CommitPageSize());
 }