Issue 8742. Preserve leading line comments during java2dart translation.

pkg/analyzer/lib/src/generated/source_io.dart

 // Copyright (c) 2014, 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.source.io;
 
 import 'source.dart';
@@ skipping 93 matching lines @@
     this._contentCache = contentCache;
     this._file = file;
     this._uriKind = uriKind;
   }
 
   bool operator ==(Object object) => object != null && this.runtimeType == object.runtimeType && _file == (object as FileBasedSource)._file;
 
   bool exists() => _contentCache.getContents(this) != null || (_file.exists() && !_file.isDirectory());
 
   void getContents(Source_ContentReceiver receiver) {
+    //
+    // First check to see whether our content cache has an override for our contents.
+    //
     String contents = _contentCache.getContents(this);
     if (contents != null) {
       receiver.accept2(contents, _contentCache.getModificationStamp(this));
       return;
     }
+    //
+    // If not, read the contents from the file using native I/O.
+    //
     getContentsFromFile(receiver);
   }
 
   String get encoding {
     if (_encoding == null) {
       _encoding = "${_uriKind.encoding}${_file.toURI().toString()}";
     }
     return _encoding;
   }
 
@@ skipping 119 matching lines @@
     if (path == null) {
       path = uri.path;
       if (path == null) {
         return null;
       }
     }
     String pkgName;
     String relPath;
     int index = path.indexOf('/');
     if (index == -1) {
+      // No slash
       pkgName = path;
       relPath = "";
     } else if (index == 0) {
+      // Leading slash is invalid
       return null;
     } else {
+      // <pkgName>/<relPath>
       pkgName = path.substring(0, index);
       relPath = path.substring(index + 1);
     }
     for (JavaFile packagesDirectory in _packagesDirectories) {
       JavaFile resolvedFile = new JavaFile.relative(packagesDirectory, path);
       if (resolvedFile.exists()) {
         JavaFile canonicalFile = getCanonicalFile(packagesDirectory, pkgName, relPath);
         UriKind uriKind = isSelfReference(packagesDirectory, canonicalFile) ? UriKind.PACKAGE_SELF_URI : UriKind.PACKAGE_URI;
         return new FileBasedSource.con2(contentCache, canonicalFile, uriKind);
       }
@@ skipping 150 matching lines @@
     return null;
   }
 
   Source resolveAbsolute(ContentCache contentCache, Uri uri) {
     if (!isFileUri(uri)) {
       return null;
     }
     return new FileBasedSource.con1(contentCache, new JavaFile.fromUri(uri));
   }
 }