Clean patch implementation.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

Index: sdk/lib/_internal/compiler/implementation/resolution/members.dart
diff --git a/sdk/lib/_internal/compiler/implementation/resolution/members.dart b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
index 4c3b88cee65ef56f6fd2be3d6c3738ef4b4ad89a..2e6ae95ab226867f084c913802a7ad0f9f556cb9 100644
--- a/sdk/lib/_internal/compiler/implementation/resolution/members.dart
+++ b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
@@ -322,18 +322,7 @@ class ResolverTask extends CompilerTask {
     while (!originParameters.isEmpty) {
       ParameterElementX originParameter = originParameters.head;
       ParameterElementX patchParameter = patchParameters.head;
-      // TODO(johnniwinther): Remove the case for reassignment of
-      // [patch]/[origin] when resolution is ensure to be done only once.
-      assert(invariant(originParameter, originParameter.origin == null));
-      assert(invariant(originParameter,
-          originParameter.patch == null ||
-          originParameter.patch == patchParameter));
-      originParameter.patch = patchParameter;
-      assert(invariant(patchParameter,
-          patchParameter.origin == null ||
-          patchParameter.origin == originParameter));
-      assert(invariant(patchParameter, patchParameter.patch == null));
-      patchParameter.origin = originParameter;
+      originParameter.applyPatch(patchParameter);
       DartType originParameterType = originParameter.computeType(compiler);
       DartType patchParameterType = patchParameter.computeType(compiler);
       if (originParameterType != patchParameterType) {