Explicit conversions for Float32 array loads/stores.

runtime/vm/flow_graph_type_propagator.cc

Index: runtime/vm/flow_graph_type_propagator.cc
===================================================================
--- runtime/vm/flow_graph_type_propagator.cc	(revision 32793)
+++ runtime/vm/flow_graph_type_propagator.cc	(working copy)
@@ -1226,6 +1226,17 @@
 }
 
 
+CompileType FloatToDoubleInstr::ComputeType() const {
+  return CompileType::FromCid(kDoubleCid);
+}
+
+
+CompileType DoubleToFloatInstr::ComputeType() const {
+  // Type is double when converted back.
+  return CompileType::FromCid(kDoubleCid);
+}
+
+
 CompileType InvokeMathCFunctionInstr::ComputeType() const {
   return CompileType::FromCid(kDoubleCid);
 }