Add no-info mappings at start of out.js and after mapped functions

tests/compiler/dart2js/sourcemaps/stacktrace_test.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/compiler_new.dart';
@@ skipping 98 matching lines @@
   try {
     @{2:test}throw '$EXCEPTION_MARKER';
   } on String catch (e) {
     rethrow;
   }
 }
 ''',
   '''
 import 'package:expect/expect.dart';
 main() {
+  @{1:main}test(new Class());
+}
+@NoInline()
+test(c) {
+  @{2:test}c.field.method();

[Johnni Winther, 2017/01/25 10:44:20]

Previously the stack trace for this would wrongfully contain mapped frames from
boilerplate code.

[Siggi Cherem (dart-lang), 2017/01/25 16:15:09]

What did the frames look like before?

I'm guessing we want to do something about interceptors for the bug in
https://github.com/dart-lang/sdk/issues/28442, but would this change at least
mean that we no longer have an incorrect mapping to trim()?

[Johnni Winther, 2017/01/26 09:59:14]

It had multiple occurrences of the 'test' frame (for instance from
init.currentScript). The test doesn't scrutinize this. I follow up in other CL -
also verifying the status of 28442.

+}
+class Class {
+  var field;
+}
+''',
+  '''
+import 'package:expect/expect.dart';
+main() {
   // This call is no longer on the stack when the error is thrown.
   @{:main}test();
 }
 @NoInline()
 test() async {
   @{1:test}throw '$EXCEPTION_MARKER';
 }
 ''',
   '''
 import 'package:expect/expect.dart';
@@ skipping 172 matching lines @@
   print("Running d8 $output");
   ProcessResult runResult = Process.runSync(d8executable,
       ['sdk/lib/_internal/js_runtime/lib/preambles/d8.js', output]);
   String out = '${runResult.stderr}\n${runResult.stdout}';
   if (verbose) {
     print('d8 output:');
     print(out);
   }
   List<String> lines = out.split(new RegExp(r'(\r|\n|\r\n)'));
   List<StackTraceLine> jsStackTrace = <StackTraceLine>[];
-  bool seenMarker = false;
   for (String line in lines) {
-    if (seenMarker) {
-      line = line.trim();
-      if (line.startsWith('at ')) {
-        jsStackTrace.add(new StackTraceLine.fromText(line));
-      }
-    } else if (line == EXCEPTION_MARKER) {
-      seenMarker = true;
+    if (line.startsWith('    at ')) {
+      jsStackTrace.add(new StackTraceLine.fromText(line));
     }
   }
 
   List<StackTraceLine> dartStackTrace = <StackTraceLine>[];
   for (StackTraceLine line in jsStackTrace) {
     TargetEntry targetEntry = _findColumn(line.lineNo - 1, line.columnNo - 1,
         _findLine(sourceMap, line.lineNo - 1));
-    if (targetEntry == null) {
+    if (targetEntry == null || targetEntry.sourceUrlId == null) {
       dartStackTrace.add(line);
     } else {
       String methodName;
-      if (targetEntry.sourceNameId != 0) {
+      if (targetEntry.sourceNameId != null) {
         methodName = sourceMap.names[targetEntry.sourceNameId];
       }
       String fileName;
-      if (targetEntry.sourceUrlId != 0) {
+      if (targetEntry.sourceUrlId != null) {
         fileName = sourceMap.urls[targetEntry.sourceUrlId];
       }
       dartStackTrace.add(new StackTraceLine(methodName, fileName,
           targetEntry.sourceLine + 1, targetEntry.sourceColumn + 1));
     }
   }
 
   int expectedIndex = 0;
   List<StackTraceLine> unexpectedLines = <StackTraceLine>[];
   for (StackTraceLine line in dartStackTrace) {
@@ skipping 149 matching lines @@
 String get d8executable {
   if (Platform.isWindows) {
     return 'third_party/d8/windows/d8.exe';
   } else if (Platform.isLinux) {
     return 'third_party/d8/linux/d8';
   } else if (Platform.isMacOS) {
     return 'third_party/d8/macos/d8';
   }
   throw new UnsupportedError('Unsupported platform.');
 }