Fixing Heap::Available() to return total of all spaces.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 99f2e93f505f78a4d3894f828083d41b42d3decd..50b26820dfeccc7a4db37027e6bd9ec52f022857 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -227,8 +227,12 @@ void Heap::UpdateMaximumCommitted() {
 intptr_t Heap::Available() {
   if (!HasBeenSetUp()) return 0;
 
-  return new_space_.Available() + old_space_->Available() +
-         code_space_->Available() + map_space_->Available();
+  intptr_t total = 0;
+  AllSpaces spaces(this);
+  for (Space* space = spaces.next(); space != NULL; space = spaces.next()) {
+    total += space->Available();
+  }
+  return total;
 }