Revert "New implementation of {,Linked}Hash{Set,Map}."

sdk/lib/_internal/compiler/implementation/ssa/variable_allocator.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/variable_allocator.dart
diff --git a/sdk/lib/_internal/compiler/implementation/ssa/variable_allocator.dart b/sdk/lib/_internal/compiler/implementation/ssa/variable_allocator.dart
index 423bdc9e5fefbd6d5fc90bdc31abaf1826b6275c..34f960d2dda68ea940bc8a3223ae16b5bf1cbab4 100644
--- a/sdk/lib/_internal/compiler/implementation/ssa/variable_allocator.dart
+++ b/sdk/lib/_internal/compiler/implementation/ssa/variable_allocator.dart
@@ -299,8 +299,7 @@ class SsaLiveIntervalBuilder extends HBaseVisitor {
     int lastId = env.loopMarkers[header];
     // Update all instructions that are liveIns in [header] to have a
     // range that covers the loop.
-    new Map.from(env.liveInstructions).forEach((HInstruction instruction,
-                                                int id) {
+    env.liveInstructions.forEach((HInstruction instruction, int id) {
       LiveInterval range = env.liveIntervals.putIfAbsent(
           instruction, () => new LiveInterval());
       range.loopUpdate(env.startId, lastId);