Refactor handling of source map information.

pkg/compiler/lib/src/ssa/optimize.dart

Index: pkg/compiler/lib/src/ssa/optimize.dart
diff --git a/pkg/compiler/lib/src/ssa/optimize.dart b/pkg/compiler/lib/src/ssa/optimize.dart
index 9aa51f0d21e1b0f8ab51293b1fbabb625c6fedc3..04ac400d3229acfbe04644275d195a19cc9854be 100644
--- a/pkg/compiler/lib/src/ssa/optimize.dart
+++ b/pkg/compiler/lib/src/ssa/optimize.dart
@@ -167,8 +167,8 @@ class SsaInstructionSimplifier extends HBaseVisitor
         if (replacement.sourceElement == null) {
           replacement.sourceElement = instruction.sourceElement;
         }
-        if (replacement.sourcePosition == null) {
-          replacement.sourcePosition = instruction.sourcePosition;
+        if (replacement.sourceInformation == null) {
+          replacement.sourceInformation = instruction.sourceInformation;
         }
         if (!replacement.isInBasicBlock()) {
           // The constant folding can return an instruction that is already