Adding V8 api to get memory statistics of spaces in V8::Heap.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 5dfae06c3ab1bd01dc673e3005fb7f923207fb49..1037600e1b17825ec7e6e768fc2757ce0c892ee0 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -664,6 +664,19 @@ class Heap {
     }
     return NULL;
   }
+  Space* space(int idx) {
+    switch (idx) {
+      case NEW_SPACE:
+        return new_space();
+      case LO_SPACE:
+        return lo_space();
+      default:
+        return paged_space(idx);
+    }
+  }
+
+  // Returns name of the space.
+  const char* GetSpaceName(int idx);
 
   bool always_allocate() { return always_allocate_scope_depth_ != 0; }
   Address always_allocate_scope_depth_address() {