Disable type erasure during strong mode tests.

pkg/front_end/lib/src/fasta/kernel/kernel_target.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
index 4be81b7332951d2f609d1a8f4a711a73f26d3d81..ec672cb60728db1a4e004e279ef04f89bf385c70 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
@@ -686,8 +686,10 @@ class KernelTarget extends TargetImplementation {
 
   void otherTransformations() {
     // TODO(ahe): Don't generate type variables in the first place.
-    program.accept(new Erasure());
-    ticker.logMs("Erased type variables in generic methods");
+    if (!strongMode) {
+      program.accept(new Erasure());
+      ticker.logMs("Erased type variables in generic methods");
+    }
     // TODO(kmillikin): Make this run on a per-method basis.
     transformAsync.transformProgram(program);
     ticker.logMs("Transformed async methods");