Fix crash https://code.google.com/p/dart/issues/detail?id=11793: only compute a range for a loop if…

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

Index: sdk/lib/_internal/compiler/implementation/ssa/value_range_analyzer.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/ssa/value_range_analyzer.dart	(revision 25009)
+++ sdk/lib/_internal/compiler/implementation/ssa/value_range_analyzer.dart	(working copy)
@@ -615,6 +615,11 @@
 
   Range visitPhi(HPhi phi) {
     if (!phi.isInteger()) return info.newUnboundRange();
+    // Some phases may replace instructions that change the inputs of
+    // this phi. Only the [SsaTypesPropagation] phase will update the
+    // phi type. Play it safe by assuming the [SsaTypesPropagation]
+    // phase is not necessarily run before the [ValueRangeAnalyzer].
+    if (phi.inputs.any((i) => !i.isInteger())) return info.newUnboundRange();
     if (phi.block.isLoopHeader()) {
       Range range = tryInferLoopPhiRange(phi);
       if (range == null) return info.newUnboundRange();