Make JSFunction::BodyDescriptor the only single place that knows how to iterate JSFunction's body.

src/profiler/heap-snapshot-generator.cc

 // Copyright 2013 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.
 
 #include "src/profiler/heap-snapshot-generator.h"
 
 #include "src/code-stubs.h"
 #include "src/conversions.h"
 #include "src/debug/debug.h"
 #include "src/profiler/allocation-tracker.h"
@@ skipping 1140 matching lines @@
     SetInternalReference(js_fun, entry,
                          "shared", shared_info,
                          JSFunction::kSharedFunctionInfoOffset);
     TagObject(js_fun->context(), "(context)");
     SetInternalReference(js_fun, entry,
                          "context", js_fun->context(),
                          JSFunction::kContextOffset);
     SetWeakReference(js_fun, entry,
                      "next_function_link", js_fun->next_function_link(),
                      JSFunction::kNextFunctionLinkOffset);
-    STATIC_ASSERT(JSFunction::kNextFunctionLinkOffset
-                 == JSFunction::kNonWeakFieldsEndOffset);
+    // Ensure no new weak references appeared in JSFunction.
+    STATIC_ASSERT(JSFunction::kCodeEntryOffset ==
+                  JSFunction::kNonWeakFieldsEndOffset);
+    STATIC_ASSERT(JSFunction::kCodeEntryOffset + kPointerSize ==
+                  JSFunction::kNextFunctionLinkOffset);
     STATIC_ASSERT(JSFunction::kNextFunctionLinkOffset + kPointerSize
                  == JSFunction::kSize);
   } else if (obj->IsJSGlobalObject()) {
     JSGlobalObject* global_obj = JSGlobalObject::cast(obj);
     SetInternalReference(global_obj, entry, "native_context",
                          global_obj->native_context(),
                          JSGlobalObject::kNativeContextOffset);
     SetInternalReference(global_obj, entry, "global_proxy",
                          global_obj->global_proxy(),
                          JSGlobalObject::kGlobalProxyOffset);
@@ skipping 1994 matching lines @@
   for (int i = 1; i < sorted_strings.length(); ++i) {
     writer_->AddCharacter(',');
     SerializeString(sorted_strings[i]);
     if (writer_->aborted()) return;
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8