[heap] Scavenger: Allow more tasks on arm

Bug: chromium:738865
Change-Id: I17f01ae4e4c854a8ca674f4fa1647d281ecede9c
Reviewed-on: https://chromium-review.googlesource.com/730743Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48792}

src/heap/heap.h

@@ -1647,11 +1647,7 @@ class Heap {
 
   static const int kInitialFeedbackCapacity = 256;
 
-#ifdef V8_TARGET_ARCH_ARM
-  static const int kMaxScavengerTasks = 2;
-#else
   static const int kMaxScavengerTasks = 8;
-#endif
 
   Heap();