Make lines and columns one-based in SourceLocation.

pkg/compiler/lib/src/io/source_map_builder.dart

Index: pkg/compiler/lib/src/io/source_map_builder.dart
diff --git a/pkg/compiler/lib/src/io/source_map_builder.dart b/pkg/compiler/lib/src/io/source_map_builder.dart
index de2abfb052e46820342f2551b3788d8b2f0ce9ac..df5866daa7e9f0fa05454bbaaad85937f63eb615 100644
--- a/pkg/compiler/lib/src/io/source_map_builder.dart
+++ b/pkg/compiler/lib/src/io/source_map_builder.dart
@@ -63,7 +63,7 @@ class SourceMapBuilder {
               sourceLocationMap.putIfAbsent(location.sourceUri,
                   () => new LineColumnMap<SourceMapEntry>());
           sourceLineColumnMap.add(
-              location.line, location.column, sourceMapEntry);
+              location.line - 1, location.column - 1, sourceMapEntry);
         }
       }
     });
@@ -157,8 +157,8 @@ class SourceMapBuilder {
       Uri sourceUri = sourceLocation.sourceUri;
       if (sourceUri != null) {
         sourceUriIndexEncoder.encode(output, uriMap[sourceUri]);
-        sourceLineEncoder.encode(output, sourceLocation.line);
-        sourceColumnEncoder.encode(output, sourceLocation.column);
+        sourceLineEncoder.encode(output, sourceLocation.line - 1);
+        sourceColumnEncoder.encode(output, sourceLocation.column - 1);
       }
 
       String sourceName = sourceLocation.sourceName;