Let CSP-mode-flag be available as a foreign_helper constant.

pkg/compiler/lib/src/ssa/builder.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of ssa;
 
 class SsaFunctionCompiler implements FunctionCompiler {
   SsaCodeGeneratorTask generator;
   SsaBuilderTask builder;
   SsaOptimizerTask optimizer;
@@ skipping 3693 matching lines @@
        return;
      }
      ast.LiteralString string = argument.asLiteralString();
      if (string == null) {
        compiler.reportError(
            argument, MessageKind.GENERIC,
            {'text': 'Error: Expected a literal string.'});
      }
      String name = string.dartString.slowToString();
      bool value = false;
-     if (name == 'MUST_RETAIN_METADATA') {
-       value = backend.mustRetainMetadata;
-     } else {
-       compiler.reportError(
-           node, MessageKind.GENERIC,
-           {'text': 'Error: Unknown internal flag "$name".'});
+     switch (name) {
+       case 'MUST_RETAIN_METADATA':
+         value = backend.mustRetainMetadata;
+         break;
+       case 'USE_CONTENT_SECURITY_POLICY':
+         value = compiler.useContentSecurityPolicy;
+         break;
+       default:
+         compiler.reportError(
+             node, MessageKind.GENERIC,
+             {'text': 'Error: Unknown internal flag "$name".'});
      }
      stack.add(graph.addConstantBool(value, compiler));
   }
 
   void handleForeignJsGetName(ast.Send node) {
     List<ast.Node> arguments = node.arguments.toList();
     ast.Node argument;
     switch (arguments.length) {
     case 0:
       compiler.reportError(
@@ skipping 3192 matching lines @@
     if (unaliased is TypedefType) throw 'unable to unalias $type';
     unaliased.accept(this, builder);
   }
 
   void visitDynamicType(DynamicType type, SsaBuilder builder) {
     JavaScriptBackend backend = builder.compiler.backend;
     ClassElement cls = backend.findHelper('DynamicRuntimeType');
     builder.push(new HDynamicType(type, new TypeMask.exact(cls, classWorld)));
   }
 }