[Isolates] Merge 6700:7030 from bleeding_edge to isolates.

src/spaces.h

Index: src/spaces.h
===================================================================
--- src/spaces.h	(revision 7006)
+++ src/spaces.h	(working copy)
@@ -2106,6 +2106,12 @@
     accounting_stats_.DeallocateBytes(accounting_stats_.Size());
     accounting_stats_.AllocateBytes(new_size);
 
+    // Flush allocation watermarks.
+    for (Page* p = first_page_; p != top_page; p = p->next_page()) {
+      p->SetAllocationWatermark(p->AllocationTop());
+    }
+    top_page->SetAllocationWatermark(new_top);
+
 #ifdef DEBUG
     if (FLAG_enable_slow_asserts) {
       intptr_t actual_size = 0;