Improve the memory consumption and performance of our string buffer implementation.

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 4041 matching lines @@
 ''');
         }
       }
 
       emitMain(mainBuffer);
       emitInitFunction(mainBuffer);
       if (!areAnyElementsDeferred) {
         mainBuffer.add('})()$n');
       }
       compiler.assembledCode = mainBuffer.getText();
-      outputSourceMap(mainBuffer, compiler.assembledCode, '');
+      outputSourceMap(compiler.assembledCode, '');
 
       emitDeferredCode();
 
     });
     return compiler.assembledCode;
   }
 
   CodeBuffer bufferForElement(Element element, CodeBuffer eagerBuffer) {
     Element owner = element.getLibrary();
     if (!element.isTopLevel() && !element.isNative()) {
@@ skipping 83 matching lines @@
     classesCollector = oldClassesCollector;
 
     if (!deferredConstants.isEmpty) {
       buffer.addBuffer(deferredConstants);
     }
 
     String code = buffer.getText();
     compiler.outputProvider('part', 'js')
       ..add(code)
       ..close();
-    outputSourceMap(buffer, compiler.assembledCode, 'part');
+    outputSourceMap(compiler.assembledCode, 'part');
   }
 
   String buildGeneratedBy() {
     var suffix = '';
     if (compiler.hasBuildId) suffix = ' version: ${compiler.buildId}';
     return '// Generated by dart2js, the Dart to JavaScript compiler$suffix.\n';
   }
 
   String buildSourceMap(CodeBuffer buffer, SourceFile compiledFile) {
     SourceMapBuilder sourceMapBuilder =
         new SourceMapBuilder(compiler.sourceMapUri);
     buffer.forEachSourceLocation(sourceMapBuilder.addMapping);
     return sourceMapBuilder.build(compiledFile);
   }
 
-  void outputSourceMap(CodeBuffer buffer, String code, String name) {
+  void outputSourceMap(String code, String name) {
     if (!generateSourceMap) return;
     SourceFile compiledFile = new SourceFile(null, compiler.assembledCode);
     String sourceMap = buildSourceMap(mainBuffer, compiledFile);
     compiler.outputProvider(name, 'js.map')
         ..add(sourceMap)
         ..close();
   }
 
   bool isDeferred(Element element) {
     return compiler.deferredLoadTask.isDeferred(element);
@@ skipping 114 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].
 """;