Optimize num::~/, num::>> and num::<< for some cases.

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

Index: sdk/lib/_internal/compiler/implementation/ssa/tracer.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/ssa/tracer.dart	(revision 31017)
+++ sdk/lib/_internal/compiler/implementation/ssa/tracer.dart	(working copy)
@@ -478,6 +478,10 @@
     return "ThrowExpression ${temporaryId(node.inputs[0])}";
   }
 
+  String visitTruncatingDivide(HTruncatingDivide node) {
+    return handleInvokeBinary(node, '~/');
+  }
+
   String visitExitTry(HExitTry node) {
     return "Exit try";
   }