Snapshot DDC trained on itself

pkg/dev_compiler/lib/src/compiler/compiler.dart

Index: pkg/dev_compiler/lib/src/compiler/compiler.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/compiler.dart b/pkg/dev_compiler/lib/src/compiler/compiler.dart
index e958e44939657332fd555cc28e7b3686b7992ab6..ac0d249aaa7769284632ef8fd35d08111238cf36 100644
--- a/pkg/dev_compiler/lib/src/compiler/compiler.dart
+++ b/pkg/dev_compiler/lib/src/compiler/compiler.dart
@@ -397,7 +397,7 @@ class CompilerOptions {
     for (var mapping in argument) {
       var splitMapping = mapping.split(',');
       if (splitMapping.length >= 2) {
-        mappings[path.absolute(splitMapping[0])] = splitMapping[1];
+        mappings[path.canonicalize(splitMapping[0])] = splitMapping[1];
       }
     }
     return mappings;
@@ -586,7 +586,7 @@ Map placeSourceMap(
   var map = new Map.from(sourceMap);
   // Convert to a local file path if it's not.
   sourceMapPath = path.fromUri(_sourceToUri(sourceMapPath));
-  var sourceMapDir = path.dirname(path.absolute(sourceMapPath));
+  var sourceMapDir = path.dirname(path.canonicalize(sourceMapPath));
   var list = new List.from(map['sources']);
   map['sources'] = list;
 
@@ -595,7 +595,7 @@ Map placeSourceMap(
     if (uri.scheme == 'dart' || uri.scheme == 'package') return sourcePath;
 
     // Convert to a local file path if it's not.
-    sourcePath = path.absolute(path.fromUri(uri));
+    sourcePath = path.canonicalize(path.fromUri(uri));
 
     // Allow bazel mappings to override.
     var match = bazelMappings[sourcePath];
@@ -628,6 +628,6 @@ Uri _sourceToUri(String source) {
       return uri;
     default:
       // Assume a file path.
-      return new Uri.file(path.absolute(source));
+      return new Uri.file(path.canonicalize(source));
   }
 }