New insertion write barrier.

BUG=

Review URL: https://codereview.chromium.org/1073953006

Cr-Commit-Position: refs/heads/master@{#28199}

src/heap/incremental-marking-inl.h

@@ -16,24 +16,8 @@ bool IncrementalMarking::BaseRecordWrite(HeapObject* obj, Object** slot,
   HeapObject* value_heap_obj = HeapObject::cast(value);
   MarkBit value_bit = Marking::MarkBitFrom(value_heap_obj);
   if (Marking::IsWhite(value_bit)) {
-    MarkBit obj_bit = Marking::MarkBitFrom(obj);
-    if (Marking::IsBlack(obj_bit)) {
-      MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
-      if (chunk->IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR)) {
-        if (chunk->IsLeftOfProgressBar(slot)) {
     WhiteToGreyAndPush(value_heap_obj, value_bit);
     RestartIfNotMarking();
-        } else {
-          return false;
-        }
-      } else {
-        BlackToGreyAndUnshift(obj, obj_bit);
-        RestartIfNotMarking();
-        return false;
-      }
-    } else {
-      return false;
-    }
   }
   if (!is_compacting_) return false;
   MarkBit obj_bit = Marking::MarkBitFrom(obj);

src/heap/spaces.h

@@ -508,13 +508,6 @@ class MemoryChunk {
     }
   }
 
-  bool IsLeftOfProgressBar(Object** slot) {
-    Address slot_address = reinterpret_cast<Address>(slot);
-    DCHECK(slot_address > this->address());
-    return (slot_address - (this->address() + kObjectStartOffset)) <
-           progress_bar();
-  }
-
   static void IncrementLiveBytesFromGC(Address address, int by) {
     MemoryChunk::FromAddress(address)->IncrementLiveBytes(by);
   }