Introduce explicit constant for per Context debug data set by embedder

src/compiler.cc

 // 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.
 
 #include "src/v8.h"
 
 #include "src/compiler.h"
 
 #include "src/ast-numbering.h"
 #include "src/bootstrapper.h"
@@ skipping 1045 matching lines @@
 
 static Handle<SharedFunctionInfo> CompileToplevel(CompilationInfo* info) {
   Isolate* isolate = info->isolate();
   PostponeInterruptsScope postpone(isolate);
   DCHECK(!isolate->native_context().is_null());
   ParseInfo* parse_info = info->parse_info();
   Handle<Script> script = parse_info->script();
 
   // TODO(svenpanne) Obscure place for this, perhaps move to OnBeforeCompile?
   FixedArray* array = isolate->native_context()->embedder_data();
-  script->set_context_data(array->get(0));
+  script->set_context_data(array->get(v8::Context::kDebugIdIndex));
 
   isolate->debug()->OnBeforeCompile(script);
 
   DCHECK(parse_info->is_eval() || parse_info->is_global() ||
          parse_info->is_module());
 
   parse_info->set_toplevel();
 
   Handle<SharedFunctionInfo> result;
 
@@ skipping 520 matching lines @@
   parse_info_ = nullptr;
 }
 
 #if DEBUG
 void CompilationInfo::PrintAstForTesting() {
   PrintF("--- Source from AST ---\n%s\n",
          PrettyPrinter(isolate(), zone()).PrintProgram(function()));
 }
 #endif
 } }  // namespace v8::internal