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

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 
 #include "src/allocation.h"
@@ skipping 643 matching lines @@
         return map_space();
       case CODE_SPACE:
         return code_space();
       case NEW_SPACE:
       case LO_SPACE:
         UNREACHABLE();
     }
     return NULL;
   }
 
+  // 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() {
     return reinterpret_cast<Address>(&always_allocate_scope_depth_);
   }
 
   Address* NewSpaceAllocationTopAddress() {
     return new_space_.allocation_top_address();
   }
   Address* NewSpaceAllocationLimitAddress() {
     return new_space_.allocation_limit_address();
@@ skipping 1924 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_H_