Revert of [heap] Start sweeper tasks after evacuation.

src/heap/mark-compact.h

Index: src/heap/mark-compact.h
diff --git a/src/heap/mark-compact.h b/src/heap/mark-compact.h
index 19d72fc7d5e280456f6b1453bacb9634617a770d..1e082f67c67d0199447d499c02572c4694c2e369 100644
--- a/src/heap/mark-compact.h
+++ b/src/heap/mark-compact.h
@@ -299,25 +299,24 @@
         : heap_(heap),
           pending_sweeper_tasks_semaphore_(0),
           sweeping_in_progress_(false),
+          late_pages_(false),
           num_sweeping_tasks_(0) {}
 
     bool sweeping_in_progress() { return sweeping_in_progress_; }
+    bool contains_late_pages() { return late_pages_; }
 
     void AddPage(AllocationSpace space, Page* page);
+    void AddLatePage(AllocationSpace space, Page* page);
 
     int ParallelSweepSpace(AllocationSpace identity, int required_freed_bytes,
                            int max_pages = 0);
     int ParallelSweepPage(Page* page, AllocationSpace identity);
 
-    // After calling this function sweeping is considered to be in progress
-    // and the main thread can sweep lazily, but the background sweeper tasks
-    // are not running yet.
     void StartSweeping();
-    void StartSweeperTasks();
+    void StartSweepingHelper(AllocationSpace space_to_start);
     void EnsureCompleted();
     void EnsureNewSpaceCompleted();
-    bool AreSweeperTasksRunning();
-    bool IsSweepingCompleted(AllocationSpace space);
+    bool IsSweepingCompleted();
     void SweepOrWaitUntilSweepingCompleted(Page* page);
 
     void AddSweptPageSafe(PagedSpace* space, Page* page);
@@ -344,6 +343,7 @@
     SweptList swept_list_[kAllocationSpaces];
     SweepingList sweeping_list_[kAllocationSpaces];
     bool sweeping_in_progress_;
+    bool late_pages_;
     base::AtomicNumber<intptr_t> num_sweeping_tasks_;
   };
 
@@ -643,10 +643,21 @@
 
   void AbortTransitionArrays();
 
-  // Starts sweeping of spaces by contributing on the main thread and setting
-  // up other pages for sweeping. Does not start sweeper tasks.
-  void StartSweepSpaces();
-  void StartSweepSpace(PagedSpace* space);
+  // -----------------------------------------------------------------------
+  // Phase 2: Sweeping to clear mark bits and free non-live objects for
+  // a non-compacting collection.
+  //
+  //  Before: Live objects are marked and non-live objects are unmarked.
+  //
+  //   After: Live objects are unmarked, non-live regions have been added to
+  //          their space's free list. Active eden semispace is compacted by
+  //          evacuation.
+  //
+
+  // If we are not compacting the heap, we simply sweep the spaces except
+  // for the large object space, clearing mark bits and adding unmarked
+  // regions to each space's free list.
+  void SweepSpaces();
 
   void EvacuateNewSpacePrologue();
 
@@ -669,6 +680,9 @@
 
   void ReleaseEvacuationCandidates();
 
+  // Starts sweeping of a space by contributing on the main thread and setting
+  // up other pages for sweeping.
+  void StartSweepSpace(PagedSpace* space);
 
 #ifdef DEBUG
   friend class MarkObjectVisitor;