Add empty mapping entries for the ranges of generated JavaScript that don't map to any Dart source …

lib/compiler/implementation/source_map_builder.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.
 
 #library('source_map_builder');
 
 #import('dart:json');
 
 #import('source_file.dart');
 
@@ skipping 52 matching lines @@
     buffer.add('  "sources": ');
     JSON.printOn(sourceUrlList, buffer);
     buffer.add(',\n');
     buffer.add('  "names": ');
     JSON.printOn(sourceNameList, buffer);
     buffer.add('\n}\n');
     return buffer.toString();
   }
 
   void writeEntry(_Entry entry, SourceFile targetFile, StringBuffer output) {
-    SourceFile sourceFile = entry.sourceFile;
-    if (sourceFile === null || entry.sourceOffset >= sourceFile.text.length) {
-      return;
-    }
-
     int targetLine = targetFile.getLine(entry.targetOffset);
     int targetColumn = targetFile.getColumn(targetLine, entry.targetOffset);
-    String sourceUrl = sourceFile.filename;
-    int sourceLine = sourceFile.getLine(entry.sourceOffset);
-    int sourceColumn = sourceFile.getColumn(sourceLine, entry.sourceOffset);
+    String sourceUrl;
+    int sourceLine;
+    int sourceColumn;
+    SourceFile sourceFile = entry.sourceFile;
+    // TODO(podivilov): make sure entries are always associated with the right
+    // source file.
+    if (sourceFile != null && entry.sourceOffset < sourceFile.text.length) {
+      sourceUrl = sourceFile.filename;
+      sourceLine = sourceFile.getLine(entry.sourceOffset);
+      sourceColumn = sourceFile.getColumn(sourceLine, entry.sourceOffset);
+    }
     String sourceName = entry.sourceName;
 
     if (targetLine > previousTargetLine) {
       for (int i = previousTargetLine; i < targetLine; ++i) {
         output.add(';');
       }
       previousTargetLine = targetLine;
       previousTargetColumn = 0;
       firstEntryInLine = true;
     }
@@ skipping 56 matching lines @@
 }
 
 class _Entry {
   SourceFile sourceFile;
   int sourceOffset;
   String sourceName;
   int targetOffset;
   _Entry(this.sourceFile, this.sourceOffset, this.sourceName,
          this.targetOffset);
 }