Fix a compiler error on Windows introduced by r10093

src/incremental-marking.cc

Index: src/incremental-marking.cc
diff --git a/src/incremental-marking.cc b/src/incremental-marking.cc
index c88eb01787b11eb92811ddd8b28aa29cf2853302..dd54c630733f9c74905dcd7928641e9f9e0fb2f7 100644
--- a/src/incremental-marking.cc
+++ b/src/incremental-marking.cc
@@ -773,7 +773,7 @@ void IncrementalMarking::Step(intptr_t allocated_bytes) {
   }
 
   if (state_ == SWEEPING) {
-    if (heap_->AdvanceSweepers(bytes_to_process)) {
+    if (heap_->AdvanceSweepers(static_cast<int>(bytes_to_process))) {
       bytes_scanned_ = 0;
       StartMarking(PREVENT_COMPACTION);
     }