Support scalar lists in array bounds check elimination.

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
===================================================================
--- runtime/vm/flow_graph_optimizer.cc	(revision 16324)
+++ runtime/vm/flow_graph_optimizer.cc	(working copy)
@@ -1782,8 +1782,6 @@
                                           CheckArrayBoundInstr* check);
   Definition* LoadArrayLength(CheckArrayBoundInstr* check);
 
-
-
   // Replace uses of the definition def that are dominated by instruction dom
   // with uses of other definition.
   void RenameDominatedUses(Definition* def,
@@ -2140,7 +2138,7 @@
     // It will only be used in range boundaries.
     LoadFieldInstr* length_load = new LoadFieldInstr(
         check->array()->Copy(),
-        Array::length_offset(),
+        CheckArrayBoundInstr::LengthOffsetFor(check->array_type()),
         Type::ZoneHandle(Type::SmiType()),
         true);  // Immutable.
     length_load->set_recognized_kind(MethodRecognizer::kObjectArrayLength);
@@ -2157,8 +2155,7 @@
 
 void RangeAnalysis::ConstrainValueAfterCheckArrayBound(
     Definition* defn, CheckArrayBoundInstr* check) {
-  if ((check->array_type() != kArrayCid) &&
-      (check->array_type() != kImmutableArrayCid)) {
+  if (!CheckArrayBoundInstr::IsFixedLengthArrayType(check->array_type())) {
     return;
   }