[heap] Use RAIL mode for starting incremental marking.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index f987aaab9b606cbf818d5d4d2fca7f8ae803b4a7..ccd96511daa0a40977e04f6359a960bc87f14c7b 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -1854,7 +1854,7 @@ class Heap {
   // This constant limits the effect of load RAIL mode on GC.
   // The value is arbitrary and chosen as the largest load time observed in
   // v8 browsing benchmarks.
-  static const int kMaxLoadTimeMs = 3000;
+  static const int kMaxLoadTimeMs = 7000;
 
   bool ShouldOptimizeForLoadTime();