Make String::Empty inlineable.

src/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1405 matching lines @@
 
     kSymbolTableRootIndex,
     kStrongRootListLength = kSymbolTableRootIndex,
     kRootListLength
   };
 
   STATIC_CHECK(kUndefinedValueRootIndex == Internals::kUndefinedValueRootIndex);
   STATIC_CHECK(kNullValueRootIndex == Internals::kNullValueRootIndex);
   STATIC_CHECK(kTrueValueRootIndex == Internals::kTrueValueRootIndex);
   STATIC_CHECK(kFalseValueRootIndex == Internals::kFalseValueRootIndex);
+  STATIC_CHECK(kempty_symbolRootIndex == Internals::kEmptySymbolRootIndex);
 
   MUST_USE_RESULT MaybeObject* NumberToString(
       Object* number, bool check_number_string_cache = true);
   MUST_USE_RESULT MaybeObject* Uint32ToString(
       uint32_t value, bool check_number_string_cache = true);
 
   Map* MapForExternalArrayType(ExternalArrayType array_type);
   RootListIndex RootIndexForExternalArrayType(
       ExternalArrayType array_type);
 
@@ skipping 1283 matching lines @@
   AssertNoAllocation no_alloc;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG || LIVE_OBJECT_LIST
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_