Fix 64-bit compile.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index 5c8c767edc9d3ceb60727b5db481db2952775f1f..91bb9d0e068d7e506fdcbd2b47f0a06be4848296 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -3974,14 +3974,14 @@ static inline Address StartOfLiveObject(Address block_address, uint32_t cell) {
 
 // Force instantiation of templatized SweepConservatively method for
 // SWEEP_ON_MAIN_THREAD mode.
-template intptr_t MarkCompactCollector::
+template int MarkCompactCollector::
     SweepConservatively<MarkCompactCollector::SWEEP_ON_MAIN_THREAD>(
         PagedSpace*, FreeList*, Page*);
 
 
 // Force instantiation of templatized SweepConservatively method for
 // SWEEP_IN_PARALLEL mode.
-template intptr_t MarkCompactCollector::
+template int MarkCompactCollector::
     SweepConservatively<MarkCompactCollector::SWEEP_IN_PARALLEL>(
         PagedSpace*, FreeList*, Page*);