Move types out of the HInstructions.

lib/compiler/implementation/ssa/types.dart

Index: lib/compiler/implementation/ssa/types.dart
diff --git a/lib/compiler/implementation/ssa/types.dart b/lib/compiler/implementation/ssa/types.dart
index 84c857203375d1c7f53a2f23cb2c780fe80f62b8..d56aab7ed9a736d4b8a1bcd980ad1d40fbcd2786 100644
--- a/lib/compiler/implementation/ssa/types.dart
+++ b/lib/compiler/implementation/ssa/types.dart
@@ -762,3 +762,19 @@ class HBoundedPotentialPrimitiveString extends HBoundedPotentialPrimitiveType {
     return super.intersection(other);
   }
 }
+
+class HTypeMap {
+  Map<HInstruction, HType> _map;
+
+  HTypeMap() : _map = new Map<HInstruction, HType>();
+
+  operator [](HInstruction instruction) {
+    HType result = _map[instruction];
+    if (result == null) return instruction.guaranteedType;
+    return result;
+  }
+
+  operator []=(HInstruction instruction, HType value) {
+    _map[instruction] = value;
+  }
+}