Move source maps package to the dart repo, so it can be used by other internal

pkg/source_maps/test/common.dart

+// Copyright (c) 2013, 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.
+
+/// Common input/output used by builder, parser and end2end tests
+library test.common;
+
+import 'package:source_maps/source_maps.dart';
+import 'package:unittest/unittest.dart';
+
+/// Content of the source file
+const String INPUT = '''
+/** this is a comment. */
+int longVar1 = 3;
+
+// this is a comment too
+int longName(int longVar2) {
+  return longVar1 + longVar2;
+}
+''';
+var input = new SourceFile.text('input.dart', INPUT);
+
+/// A span in the input file
+Span ispan(int start, int end, [bool isIdentifier = false]) =>
+    new FileSpan(input, start, end, isIdentifier);
+
+Span inputVar1 = ispan(30, 38, true);
+Span inputFunction = ispan(74, 82, true);
+Span inputVar2 = ispan(87, 95, true);
+Span inputExpr = ispan(108, 127);
+
+/// Content of the target file
+const String OUTPUT = '''
+var x = 3;
+f(y) => x + y;
+''';
+var output = new SourceFile.text('output.dart', OUTPUT);
+
+/// A span in the output file
+Span ospan(int start, int end, [bool isIdentifier = false]) =>
+    new FileSpan(output, start, end, isIdentifier);
+
+Span outputVar1 = ospan(4, 5, true);
+Span outputFunction = ospan(11, 12, true);
+Span outputVar2 = ospan(13, 14, true);
+Span outputExpr = ospan(19, 24);
+
+/// Expected output mapping when recording the following four mappings:
+///      inputVar1       <=   outputVar1
+///      inputFunction   <=   outputFunction
+///      inputVar2       <=   outputVar2
+///      inputExpr       <=   outputExpr
+///
+/// This mapping is stored in the tests so we can independently test the builder
+/// and parser algorithms without relying entirely on end2end tests.
+const Map<String, dynamic> EXPECTED_MAP = const {
+    'version': 3,
+    'sourceRoot': '',
+    'sources': const ['input.dart'],
+    'names': const ['longVar1','longName','longVar2'],
+    'mappings': 'IACIA;AAGAC,EAAaC,MACR',
+    'file': 'output.dart'
+};
+
+check(Span outputSpan, Mapping mapping, Span inputSpan, bool realOffsets) {
+  var line = outputSpan.start.line;
+  var column = outputSpan.start.column;
+  var files = realOffsets ? {'input.dart': input} : null; 
+  var span = mapping.spanFor(line, column, files: files);
+  var span2 = mapping.spanForLocation(outputSpan.start, files: files);
+
+  // Both mapping APIs are equivalent.
+  expect(span.start.offset, span2.start.offset);
+  expect(span.start.line, span2.start.line);
+  expect(span.start.column, span2.start.column);
+  expect(span.end.offset, span2.end.offset);
+  expect(span.end.line, span2.end.line);
+  expect(span.end.column, span2.end.column);
+
+  // Mapping matches our input location (modulo using real offsets)
+  expect(span.start.line, inputSpan.start.line);
+  expect(span.start.column, inputSpan.start.column);
+  expect(span.sourceUrl, inputSpan.sourceUrl);
+  expect(span.start.offset, realOffsets ? inputSpan.start.offset : 0);
+
+  // Mapping includes the identifier, if any
+  if (inputSpan.isIdentifier) {
+    expect(span.end.line, inputSpan.end.line);
+    expect(span.end.column, inputSpan.end.column);
+    expect(span.end.offset, span.start.offset + inputSpan.text.length);
+    if (realOffsets) expect(span.end.offset, inputSpan.end.offset);
+  } else {
+    expect(span.end.offset, span.start.offset);
+    expect(span.end.line, span.start.line);
+    expect(span.end.column, span.start.column);
+  }
+}