Create html if needed in server mode

lib/src/in_memory.dart

Index: lib/src/in_memory.dart
diff --git a/lib/src/in_memory.dart b/lib/src/in_memory.dart
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+++ b/lib/src/in_memory.dart
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+// Copyright (c) 2015, 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.
+
+library dev_compiler.src.in_memory;
+
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/engine.dart' show TimestampedData;
+import 'package:analyzer/src/generated/source.dart';
+import 'package:path/path.dart' as path;
+import 'package:source_span/source_span.dart';
+
+import 'dependency_graph.dart' show runtimeFilesForServerMode;
+
+/// Uri resolver that can load test files from memory.
+class InMemoryUriResolver extends UriResolver {
+  final Map<Uri, InMemorySource> files = <Uri, InMemorySource>{};
+
+  /// Whether to represent a non-existing file with a [TestSource] (default
+  /// behavior from analyzer), or to use null (possible when overriding the
+  /// package-url-resolvers.)
+  final bool representNonExistingFiles;
+
+  InMemoryUriResolver(Map<String, String> allFiles,
+      {this.representNonExistingFiles: true}) {
+    allFiles.forEach((key, value) {
+      var uri = key.startsWith('package:') ? Uri.parse(key) : new Uri.file(key);
+      files[uri] = new InMemorySource(uri, value);
+    });
+
+    // TODO(vsm): Separate flag here?
+    if (representNonExistingFiles) {
+      runtimeFilesForServerMode.forEach((filepath) {
+        var uri = Uri.parse('/dev_compiler_runtime/$filepath');
+        files[uri] =
+            new InMemorySource(uri, '/* test contents of $filepath */');
+      });
+    }
+  }
+
+  Source resolveAbsolute(Uri uri) {
+    if (uri.scheme != 'file' && uri.scheme != 'package') return null;
+    if (!representNonExistingFiles) return files[uri];
+    return files.putIfAbsent(uri, () => new InMemorySource(uri, null));
+  }
+}
+
+class InMemoryContents implements TimestampedData<String> {
+  int modificationTime;
+  String data;
+
+  InMemoryContents(this.modificationTime, this.data);
+}
+
+/// An in memory source file.
+class InMemorySource implements Source {
+  final Uri uri;
+  InMemoryContents contents;
+  final SourceFile _file;
+  final UriKind uriKind;
+
+  InMemorySource(uri, contents)
+      : uri = uri,
+        contents = new InMemoryContents(1, contents),
+        _file = contents != null ? new SourceFile(contents, url: uri) : null,
+        uriKind = uri.scheme == 'file' ? UriKind.FILE_URI : UriKind.PACKAGE_URI;
+
+  bool exists() => contents.data != null;
+
+  Source get source => this;
+
+  String _encoding;
+  String get encoding => _encoding != null ? _encoding : (_encoding = '$uri');
+
+  String get fullName => uri.path;
+
+  int get modificationStamp => contents.modificationTime;
+  String get shortName => path.basename(uri.path);
+
+  operator ==(other) => other is InMemorySource && uri == other.uri;
+  int get hashCode => uri.hashCode;
+  bool get isInSystemLibrary => false;
+
+  Uri resolveRelativeUri(Uri relativeUri) => uri.resolveUri(relativeUri);
+
+  SourceSpan spanFor(AstNode node) {
+    final begin = node is AnnotatedNode
+        ? node.firstTokenAfterCommentAndMetadata.offset
+        : node.offset;
+    return _file.span(begin, node.end);
+  }
+
+  String toString() => '[$runtimeType: $uri]';
+}