[heap] Remove unused CompactionMode flag

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index c92e1b0015a1976a5a9f24fd2fc49b18376c201e..88e6983035cd618394b2d47bc44414b2a37ad7c0 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -274,8 +274,7 @@ static void TraceFragmentation(PagedSpace* space) {
          static_cast<int>(free), static_cast<double>(free) * 100 / reserved);
 }
 
-
-bool MarkCompactCollector::StartCompaction(CompactionMode mode) {
+bool MarkCompactCollector::StartCompaction() {
   if (!compacting_) {
     DCHECK(evacuation_candidates_.length() == 0);
 
@@ -823,7 +822,7 @@ void MarkCompactCollector::Prepare() {
   // Don't start compaction if we are in the middle of incremental
   // marking cycle. We did not collect any slots.
   if (!FLAG_never_compact && !was_marked_incrementally_) {
-    StartCompaction(NON_INCREMENTAL_COMPACTION);
+    StartCompaction();
   }
 
   PagedSpaces spaces(heap());