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

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

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of ssa;
 
 /**
  * The [LiveRange] class covers a range where an instruction is live.
  */
 class LiveRange {
@@ skipping 281 matching lines @@
     if (block.isLoopHeader() && block.predecessors.length > 1) {
       updateLoopMarker(block);
     }
   }
 
   void updateLoopMarker(HBasicBlock header) {
     LiveEnvironment env = liveInstructions[header];
     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);
       env.liveInstructions[instruction] = lastId;
     });
 
     env.removeLoopMarker(header);
 
     // Update all liveIns set to contain the liveIns of [header].
     liveInstructions.forEach((HBasicBlock block, LiveEnvironment other) {
@@ skipping 347 matching lines @@
       if (!needsName(input)) {
         names.addAssignment(predecessor, input, phi);
       } else {
         names.addCopy(predecessor, input, phi);
       }
     }
 
     namer.allocateName(phi);
   }
 }