Don't rename local variables in dart_precompiled.

dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.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 js_backend;
 
 /// Enables debugging of fast/slow objects using V8-specific primitives.
 const DEBUG_FAST_OBJECTS = false;
 
 /**
@@ skipping 4136 matching lines @@
       emitInitFunction(mainBuffer);
       if (!areAnyElementsDeferred) {
         mainBuffer.add('})()\n');
       } else {
         mainBuffer.add('\n');
       }
       compiler.assembledCode = mainBuffer.getText();
       outputSourceMap(compiler.assembledCode, '');
 
       mainBuffer.write(
-          jsAst.prettyPrint(precompiledFunctionAst, compiler).getText());
+          jsAst.prettyPrint(
+              precompiledFunctionAst, compiler,
+              allowVariableMinification: false).getText());
 
       compiler.outputProvider('', 'precompiled.js')
           ..add(mainBuffer.getText())
           ..close();
 
       emitDeferredCode();
 
     });
     return compiler.assembledCode;
   }
@@ skipping 255 matching lines @@
 
 const String HOOKS_API_USAGE = """
 // The code supports the following hooks:
 // dartPrint(message)   - if this function is defined it is called
 //                        instead of the Dart [print] method.
 // dartMainRunner(main) - if this function is defined, the Dart [main]
 //                        method will not be invoked directly.
 //                        Instead, a closure that will invoke [main] is
 //                        passed to [dartMainRunner].
 """;