Respect old space allocation limit in PagedSpace::AllocateRaw.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 054ebced2a899ff2d20941a4d4b76638de122f8a..c98e8d938d782b5cd62cc6c55e604346269097ef 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -1515,6 +1515,10 @@ class ScavengeWeakObjectRetainer : public WeakObjectRetainer {
 
 void Heap::Scavenge() {
   RelocationLock relocation_lock(this);
+  // There are soft limits in the allocation code, designed to trigger a mark
+  // sweep collection by failing allocations. There is no sense in trying to
+  // trigger one during scavenge: scavenges allocation should always succeed.
+  AlwaysAllocateScope scope(isolate());
 
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) VerifyNonPointerSpacePointers(this);