Make lines and columns one-based in SourceLocation.

tests/compiler/dart2js/sourcemaps/sourcemap_html_helper.dart

 // 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.
 
 /// Helper for creating HTML visualization of the source map information
 /// generated by a [SourceMapProcessor].
 
 library sourcemap.html.helper;
 
 import 'dart:convert';
@@ skipping 469 matching lines @@
 String computeDartHtmlPart(String name, SourceFileManager sourceFileManager,
     SourceLocationCollection collection,
     {bool showAsBlock: false}) {
   const int windowSize = 3;
   StringBuffer dartCodeBuffer = new StringBuffer();
   Map<Uri, Map<int, List<SourceLocation>>> sourceLocationMap = {};
   collection.sourceLocations.forEach((SourceLocation sourceLocation) {
     Map<int, List<SourceLocation>> uriMap =
         sourceLocationMap.putIfAbsent(sourceLocation.sourceUri, () => {});
     List<SourceLocation> lineList =
-        uriMap.putIfAbsent(sourceLocation.line, () => []);
+        uriMap.putIfAbsent(sourceLocation.line - 1, () => []);
     lineList.add(sourceLocation);
   });
   sourceLocationMap.forEach((Uri uri, Map<int, List<SourceLocation>> uriMap) {
     SourceFile sourceFile = sourceFileManager.getSourceFile(uri);
     if (sourceFile == null) return;
     StringBuffer codeBuffer = new StringBuffer();
 
     int firstLineIndex;
     int lastLineIndex;
     List<int> lineIndices = uriMap.keys.toList()..sort();
@@ skipping 44 matching lines @@
         for (int line = lastLineIndex + 1; line < lineIndex; line++) {
           codeBuffer.write(lineNumber(line, width: lineNoWidth));
           codeBuffer.write(sourceFile.kernelSource.getTextLine(line + 1));
         }
       }
       String line = sourceFile.kernelSource.getTextLine(lineIndex + 1);
       locations.sort((a, b) => a.offset.compareTo(b.offset));
       for (int i = 0; i < locations.length; i++) {
         SourceLocation sourceLocation = locations[i];
         int index = collection.getIndex(sourceLocation);
-        int start = sourceLocation.column;
+        int start = sourceLocation.column - 1;
         int end = line.length;
         if (i + 1 < locations.length) {
-          end = locations[i + 1].column;
+          end = locations[i + 1].column - 1;
         }
         if (i == 0) {
           codeBuffer.write(lineNumber(lineIndex, width: lineNoWidth));
           codeBuffer.write(line.substring(0, start));
         }
         codeBuffer
             .write('<a name="${index}" style="background:${toPattern(index)};" '
                 'title="[${lineIndex + 1},${start + 1}]" '
                 'onmouseover="highlight(\'$index\');" '
                 'onmouseout="highlight();">');
@@ skipping 51 matching lines @@
       String dartCode = truncate(codePoint.dartCode, 50);
       buffer.write('<td class="code">${dartCode}</td>');
       buffer.write('<td>${escape(codePoint.sourceLocation.shortText)}</td>');
     }
     buffer.write('</tr>');
   });
   buffer.write('</table>');
 
   return buffer.toString();
 }