Avoid repeating common parts of ProgramResults.

dart/tests/try/web/program_result.dart

Index: dart/tests/try/web/program_result.dart
diff --git a/dart/tests/try/web/program_result.dart b/dart/tests/try/web/program_result.dart
index faa56516cf353eb3433438c3be1321ba43fb085f..a085a7ffb6ee4f10b02caf2ded7439fd18ae6a9f 100644
--- a/dart/tests/try/web/program_result.dart
+++ b/dart/tests/try/web/program_result.dart
@@ -4,6 +4,8 @@
 
 library trydart.test.program_result;
 
+import '../poi/source_update.dart';
+
 class ProgramResult {
   final String code;
 
@@ -17,4 +19,39 @@ class ProgramResult {
   List<String> messagesWith(String extra) {
     return new List<String>.from(messages)..add(extra);
   }
+
+  static List<ProgramResult> decode(List encodedResults) {
+    if (encodedResults.length != 2) {
+      throw new ArgumentError(
+          "Unexpected encoding of program results: $encodedResults");
+    }
+    if (encodedResults[0].length == 1) {
+      throw new ArgumentError("Trivial diff, no reason to use decode.");
+    }
+    List<String> sources = expandUpdates(encodedResults[0]);
+    List<ProgramExpectation> expectations = encodedResults[1];
+    if (sources.length != expectations.length) {
+      throw new ArgumentError(
+          "Length mismatch: ${sources.length} != ${expectations.length}");
+    }
+    List<ProgramResult> result = new List<ProgramResult>(sources.length);
+    for (int i = 0; i < sources.length; i++) {
+      result[i] = expectations[i].toResult(sources[i]);
+    }
+    return result;
+  }
+}
+
+class ProgramExpectation {
+  final List<String> messages;
+
+  final bool compileUpdatesShouldThrow;
+
+  const ProgramExpectation(
+      this.messages, {this.compileUpdatesShouldThrow: false});
+
+  ProgramResult toResult(String code) {
+    return new ProgramResult(
+        code, messages, compileUpdatesShouldThrow: compileUpdatesShouldThrow);
+  }
 }