Remove heap size filter for context disposal garbage collection.

src/heap/gc-idle-time-handler.h

Index: src/heap/gc-idle-time-handler.h
diff --git a/src/heap/gc-idle-time-handler.h b/src/heap/gc-idle-time-handler.h
index 1e87e9da17bf34f606d354eb1efdc9af4c8f4aa1..cae6936da2952f0c4fa5c18e1fad319e2421e082 100644
--- a/src/heap/gc-idle-time-handler.h
+++ b/src/heap/gc-idle-time-handler.h
@@ -106,10 +106,6 @@ class GCIdleTimeHandler {
   // Number of scavenges that will trigger start of new idle round.
   static const int kIdleScavengeThreshold;
 
-  // Heap size threshold below which we prefer mark-compact over incremental
-  // step.
-  static const size_t kSmallHeapSize = 4 * kPointerSize * MB;
-
   // That is the maximum idle time we will have during frame rendering.
   static const size_t kMaxFrameRenderingIdleTime = 16;