Changes new space allocation from simple bump pointer allocation from

runtime/vm/scavenger.h

Index: runtime/vm/scavenger.h
diff --git a/runtime/vm/scavenger.h b/runtime/vm/scavenger.h
index 1fd7c9fe2bd88b93e8f26e2c6b7964e11a0408bc..c1d68337e53e91627cf4a0e583d1d77efc3afc5c 100644
--- a/runtime/vm/scavenger.h
+++ b/runtime/vm/scavenger.h
@@ -121,6 +121,22 @@ class Scavenger {
 
   RawObject* FindObject(FindObjectVisitor* visitor) const;
 
+  uword TryAllocateNewTLAB(intptr_t size) {
+    ASSERT(Utils::IsAligned(size, kObjectAlignment));
+    ASSERT(heap_ != Dart::vm_isolate()->heap());
+    ASSERT(!scavenging_);
+    uword result = top_;
+    intptr_t remaining = end_ - top_;
+    if (remaining < size) {
+      return 0;
+    }
+    ASSERT(to_->Contains(result));
+    ASSERT((result & kObjectAlignmentMask) == object_alignment_);
+    top_ += size;
+    ASSERT(to_->Contains(top_) || (top_ == to_->end()));
+    return result;
+  }
+
   uword AllocateGC(intptr_t size) {
     ASSERT(Utils::IsAligned(size, kObjectAlignment));
     ASSERT(heap_ != Dart::vm_isolate()->heap());
@@ -143,6 +159,8 @@ class Scavenger {
     ASSERT(heap_ != Dart::vm_isolate()->heap());
     ASSERT(thread->IsMutatorThread());
     ASSERT(thread->isolate()->IsMutatorThreadScheduled());
+    ASSERT(thread->top() <= top_);
+    ASSERT(thread->end() == top_);
 #if defined(DEBUG)
     if (FLAG_gc_at_alloc) {
       ASSERT(!scavenging_);
@@ -215,7 +233,9 @@ class Scavenger {
   void AllocateExternal(intptr_t size);
   void FreeExternal(intptr_t size);
 
-  void FlushTLS() const;
+  uword FlushTLS() const;
+  void UnflushTLS(uword value) const;
+  uword FirstObjectStart() const { return to_->start() | object_alignment_; }
 
  private:
   // Ids for time and data records in Heap::GCStats.
@@ -234,7 +254,6 @@ class Scavenger {
     kToKBAfterStoreBuffer = 3
   };
 
-  uword FirstObjectStart() const { return to_->start() | object_alignment_; }
   SemiSpace* Prologue(Isolate* isolate, bool invoke_api_callbacks);
   void IterateStoreBuffers(Isolate* isolate, ScavengerVisitor* visitor);
   void IterateObjectIdTable(Isolate* isolate, ScavengerVisitor* visitor);