[heap] User safer root set accessor when possible.

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 <map>
 
@@ skipping 1228 matching lines @@
 
 #define SYMBOL_ACCESSOR(name) inline Symbol* name();
   PRIVATE_SYMBOL_LIST(SYMBOL_ACCESSOR)
 #undef SYMBOL_ACCESSOR
 
 #define SYMBOL_ACCESSOR(name, varname, description) inline Symbol* name();
   PUBLIC_SYMBOL_LIST(SYMBOL_ACCESSOR)
 #undef SYMBOL_ACCESSOR
 
   Object* root(RootListIndex index) { return roots_[index]; }
+  Handle<Object> root_handle(RootListIndex index) {
+    return Handle<Object>(&roots_[index]);
+  }
 
   // Generated code can embed this address to get access to the roots.
   Object** roots_array_start() { return roots_; }
 
   // Sets the stub_cache_ (only used when expanding the dictionary).
   void public_set_code_stubs(UnseededNumberDictionary* value) {
     roots_[kCodeStubsRootIndex] = value;
   }
 
   // Sets the non_monomorphic_cache_ (only used when expanding the dictionary).
@@ skipping 1509 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_