Fix a bug where we would emit a noSuchMethod handler in the Object class for Object methods because…

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

Index: sdk/lib/_internal/compiler/implementation/types/flat_type_mask.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/types/flat_type_mask.dart	(revision 26305)
+++ sdk/lib/_internal/compiler/implementation/types/flat_type_mask.dart	(working copy)
@@ -496,6 +496,55 @@
            });
   }
 
+  bool needsNoSuchMethodHandling(Selector selector, Compiler compiler) {
+    // A call on an empty type mask is dead code.
+    if (isEmpty && !isNullable) return false;
+    // A call on an exact mask for an abstract class is dead code.
+    if (isExact && base.element.isAbstract(compiler)) return false;
+    // If the receiver is guaranteed to have a member that
+    // matches what we're looking for, there's no need to
+    // introduce a noSuchMethod handler. It will never be called.
+    //
+    // As an example, consider this class hierarchy:
+    //
+    //                   A    <-- noSuchMethod
+    //                  / \
+    //                 C   B  <-- foo
+    //
+    // If we know we're calling foo on an object of type B we
+    // don't have to worry about the noSuchMethod method in A
+    // because objects of type B implement foo. On the other hand,
+    // if we end up calling foo on something of type C we have to
+    // add a handler for it.
+
+    // If the holders of all user-defined noSuchMethod
+    // implementations that might be applicable to the receiver
+    // type have a matching member for the current name and
+    // selector, we avoid introducing a noSuchMethod handler.
+    //
+    // As an example, consider this class hierarchy:
+    //
+    //                       A    <-- foo
+    //                      / \
+    //   noSuchMethod -->  B   C  <-- bar
+    //                     |   |
+    //                     C   D  <-- noSuchMethod
+    //
+    // When calling foo on an object of type A, we know that the
+    // implementations of noSuchMethod are in the classes B and D
+    // that also (indirectly) implement foo, so we do not need a
+    // handler for it.
+    //
+    // If we're calling bar on an object of type D, we don't need
+    // the handler either because all objects of type D implement
+    // bar through inheritance.
+    //
+    // If we're calling bar on an object of type A we do need the
+    // handler because we may have to call B.noSuchMethod since B
+    // does not implement bar.
+    return !willHit(selector, compiler);
+  }
+
   Element locateSingleElement(Selector selector, Compiler compiler) {
     if (isEmpty) return null;
     Iterable<Element> targets = compiler.world.allFunctions.filter(selector);