Better bitwise and binary arithmetic when the left operand is known to be a number.

lib/compiler/implementation/ssa/builder.dart

Index: lib/compiler/implementation/ssa/builder.dart
diff --git a/lib/compiler/implementation/ssa/builder.dart b/lib/compiler/implementation/ssa/builder.dart
index 4abba9ad1f258c5ee19d06a2f8c227cc4a13124e..c338b66c97118f7f0ae6454cefdae154aa244622 100644
--- a/lib/compiler/implementation/ssa/builder.dart
+++ b/lib/compiler/implementation/ssa/builder.dart
@@ -1107,7 +1107,7 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
     }
 
     HInstruction instruction =
-        new HTypeConversion(convertedType, original, true);
+        new HTypeConversion.checkedModeCheck(convertedType, original);
     add(instruction);
     return instruction;
   }