Refactor handling of source map information.

pkg/compiler/lib/src/js/printer.dart

Index: pkg/compiler/lib/src/js/printer.dart
diff --git a/pkg/compiler/lib/src/js/printer.dart b/pkg/compiler/lib/src/js/printer.dart
index 19d6c3f5dcad10c8cb395907b4be74a819968627..04f70e2ef33f6c7faab9e9b1c1e71690a4bb64de 100644
--- a/pkg/compiler/lib/src/js/printer.dart
+++ b/pkg/compiler/lib/src/js/printer.dart
@@ -112,18 +112,14 @@ class Printer extends Indentation implements NodeVisitor {
   }
 
   void beginSourceRange(Node node) {
-    if (node.sourcePosition != null) {
-      outBuffer.beginMappedRange();
-      outBuffer.setSourceLocation(node.sourcePosition);
+    if (node.sourceInformation != null) {
+      node.sourceInformation.beginMapping(outBuffer);
     }
   }
 
   void endSourceRange(Node node) {
-    if (node.endSourcePosition != null) {
-      outBuffer.setSourceLocation(node.endSourcePosition);
-    }
-    if (node.sourcePosition != null) {
-      outBuffer.endMappedRange();
+    if (node.sourceInformation != null) {
+      node.sourceInformation.endMapping(outBuffer);
     }
   }