Ensure the type inferrer does not infer types for runtime helpers used by the backend.

sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart

Index: sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart	(revision 26173)
+++ sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart	(working copy)
@@ -859,6 +859,9 @@
 
   bool recordType(Element analyzedElement, TypeMask type) {
     if (isNativeElement(analyzedElement)) return false;
+    if (!compiler.backend.canBeUsedForGlobalOptimizations(analyzedElement)) {
+      return false;
+    }
     assert(type != null);
     assert(analyzedElement.isField()
            || analyzedElement.isParameter()
@@ -879,6 +882,9 @@
    */
   bool recordReturnType(Element analyzedElement, TypeMask returnType) {
     if (isNativeElement(analyzedElement)) return false;
+    if (!compiler.backend.canBeUsedForGlobalOptimizations(analyzedElement)) {
+      return false;
+    }
     assert(analyzedElement.implementation == analyzedElement);
     TypeMask existing = typeInformationOf(analyzedElement).returnType;
     if (optimismState == OPTIMISTIC
@@ -1111,8 +1117,8 @@
   }
 
   bool updateParameterType(Element parameter) {
-    FunctionTypeInformation functionInfo =
-        typeInformationOf(parameter.enclosingElement);
+    Element function = parameter.enclosingElement;
+    FunctionTypeInformation functionInfo = typeInformationOf(function);
     if (functionInfo.canBeClosurized) return false;
     if (!isNotClosure(parameter.enclosingElement)) return false;