dart2js: Use frequency of occurence to sort metadata indices.

pkg/compiler/lib/src/js_backend/backend.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;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 194 matching lines @@
           break;
       }
     }
   }
 
   void markAsMustInline(FunctionElement element) {
     _cachedDecisions[element] = _mustInline;
   }
 }
 
+class DummyConstantKinds {

[karlklose, 2015/05/28 09:39:52]

I think it use sites of these constants read better if you called the class
'DummyConstantKind' and wrote the constants in all caps.

[herhut, 2015/06/01 12:09:41]

Done.

+  static const String dummyReceiver = "DUMMY_INTERCEPTOR";
+  static const String emptyValue = "EMPTY_VALUE";
+  static const String typeVariableReference = "TYPEVARIALE_REFERENCE";

[sigurdm, 2015/05/27 14:26:41]

DBC: Typo in string

[herhut, 2015/06/01 12:09:41]

Done.

+}
+
 class JavaScriptBackend extends Backend {
   static final Uri DART_JS_HELPER = new Uri(scheme: 'dart', path: '_js_helper');
   static final Uri DART_INTERCEPTORS =
       new Uri(scheme: 'dart', path: '_interceptors');
   static final Uri DART_INTERNAL =
       new Uri(scheme: 'dart', path: '_internal');
   static final Uri DART_FOREIGN_HELPER =
       new Uri(scheme: 'dart', path: '_foreign_helper');
   static final Uri DART_JS_MIRRORS =
       new Uri(scheme: 'dart', path: '_js_mirrors');
@@ skipping 1180 matching lines @@
         // the checked setter.
         if (Elements.isStaticOrTopLevel(element)) return;
       } else {
         // If the constant-handler was not able to produce a result we have to
         // go through the builder (below) to generate the lazy initializer for
         // the static variable.
         // We also need to register the use of the cyclic-error helper.
         compiler.enqueuer.codegen.registerStaticUse(getCyclicThrowHelper());
       }
     }
+
     generatedCode[element] = functionCompiler.compile(work);
   }
 
   native.NativeEnqueuer nativeResolutionEnqueuer(Enqueuer world) {
     return new native.NativeResolutionEnqueuer(world, compiler);
   }
 
   native.NativeEnqueuer nativeCodegenEnqueuer(Enqueuer world) {
     return new native.NativeCodegenEnqueuer(world, compiler, emitter);
   }
@@ skipping 1504 matching lines @@
   }
 }
 
 /// Records that [constant] is used by the element behind [registry].
 class Dependency {
   final ConstantValue constant;
   final Element annotatedElement;
 
   const Dependency(this.constant, this.annotatedElement);
 }