Use signature inheritance when method types are unchanged

test/codegen/expect/constructors.js

Index: test/codegen/expect/constructors.js
diff --git a/test/codegen/expect/constructors.js b/test/codegen/expect/constructors.js
index 305cbb6871f9082a959a4ab02a6ff346f89b8762..72f5110a72de45b2f8f0f8b21f83ec869f22c342 100644
--- a/test/codegen/expect/constructors.js
+++ b/test/codegen/expect/constructors.js
@@ -3,25 +3,21 @@ var core = dart.import(core);
 (function(exports, core) {
   'use strict';
   class A extends core.Object {}
-  dart.setSignature(A, {});
   class B extends core.Object {
     B() {
     }
   }
-  dart.setSignature(B, {});
   class C extends core.Object {
     named() {
     }
   }
   dart.defineNamedConstructor(C, 'named');
-  dart.setSignature(C, {});
   class C2 extends C {
     named() {
       super.named();
     }
   }
   dart.defineNamedConstructor(C2, 'named');
-  dart.setSignature(C2, {});
   class D extends core.Object {
     D() {
     }
@@ -29,32 +25,27 @@ var core = dart.import(core);
     }
   }
   dart.defineNamedConstructor(D, 'named');
-  dart.setSignature(D, {});
   class E extends core.Object {
     E(name) {
       this.name = name;
     }
   }
-  dart.setSignature(E, {});
   class F extends E {
     F(name) {
       super.E(name);
     }
   }
-  dart.setSignature(F, {});
   class G extends core.Object {
     G(p1) {
       if (p1 === void 0)
         p1 = null;
     }
   }
-  dart.setSignature(G, {});
   class H extends core.Object {
     H(opts) {
       let p1 = opts && 'p1' in opts ? opts.p1 : null;
     }
   }
-  dart.setSignature(H, {});
   class I extends core.Object {
     I() {
       this.name = 'default';
@@ -64,14 +55,12 @@ var core = dart.import(core);
     }
   }
   dart.defineNamedConstructor(I, 'named');
-  dart.setSignature(I, {});
   class J extends core.Object {
     J() {
       this.initialized = true;
       this.nonInitialized = null;
     }
   }
-  dart.setSignature(J, {});
   class K extends core.Object {
     K() {
       this.s = 'a';
@@ -81,27 +70,23 @@ var core = dart.import(core);
     }
   }
   dart.defineNamedConstructor(K, 'withS');
-  dart.setSignature(K, {});
   class L extends core.Object {
     L(foo) {
       this.foo = foo;
     }
   }
-  dart.setSignature(L, {});
   class M extends L {
     named(x) {
       super.L(dart.notNull(x) + 42);
     }
   }
   dart.defineNamedConstructor(M, 'named');
-  dart.setSignature(M, {});
   class N extends M {
     named(y) {
       super.named(dart.notNull(y) + 100);
     }
   }
   dart.defineNamedConstructor(N, 'named');
-  dart.setSignature(N, {});
   class P extends N {
     P(z) {
       super.named(dart.notNull(z) + 9000);
@@ -115,7 +100,6 @@ var core = dart.import(core);
   }
   dart.defineNamedConstructor(P, 'foo');
   dart.defineNamedConstructor(P, 'bar');
-  dart.setSignature(P, {});
   let Q$ = dart.generic(function(T) {
     class Q extends core.Object {
       Q(y) {