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;
   }
 }
 
+enum SyntheticConstantKind {
+  DUMMY_INTERCEPTOR,
+  EMPTY_VALUE,
+  TYPEVARIABLE_REFERENCE,
+}
+
 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 1188 matching lines @@
           return const WorldImpact();
         }
       } 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);
     return const WorldImpact();
   }
 
   native.NativeEnqueuer nativeResolutionEnqueuer(Enqueuer world) {
     return new native.NativeResolutionEnqueuer(world, compiler);
   }
 
   native.NativeEnqueuer nativeCodegenEnqueuer(Enqueuer world) {
     return new native.NativeCodegenEnqueuer(world, compiler, emitter);
@@ skipping 1532 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);
 }