Update to latest analyzer (w/ cleanup).

Bye-bye `@protected `trampolines! :)

packages/flutter/lib/src/widgets/framework.dart

@@ -465,9 +465,6 @@ abstract class StatelessWidget extends Widget {
   /// inserted into the tree in multiple places at once.
   @protected
   Widget build(BuildContext context);
-
-  /// Trampoline to make the [build] closure library-accessible.
-  WidgetBuilder get _build => build;
 }
 
 /// A widget that has mutable state.
@@ -2012,7 +2009,7 @@ abstract class ComponentElement extends BuildableElement {
 /// Instantiation of [StatelessWidget]s.
 class StatelessElement extends ComponentElement {
   StatelessElement(StatelessWidget widget) : super(widget) {
-    _builder = widget._build;
+    _builder = widget.build;
   }
 
   @override
@@ -2022,14 +2019,14 @@ class StatelessElement extends ComponentElement {
   void update(StatelessWidget newWidget) {
     super.update(newWidget);
     assert(widget == newWidget);
-    _builder = widget._build;
+    _builder = widget.build;
     _dirty = true;
     rebuild();
   }
 
   @override
   void _reassemble() {
-    _builder = widget._build;
+    _builder = widget.build;
     super._reassemble();
   }
 }

packages/flutter_test/pubspec.yaml

@@ -10,7 +10,7 @@ dependencies:
   # We don't actually depend on 'analyzer', but 'test' and 'flutter_tools' do.
   # We pin the version of analyzer we depend on to avoid version skew across our
   # packages.
-  analyzer: 0.27.4-alpha.14
+  analyzer: 0.27.4-alpha.15
 
   flutter:
     path: ../flutter

packages/flutter_tools/pubspec.yaml

@@ -38,7 +38,7 @@ dependencies:
   test: 0.12.13+5
 
   # Pinned in flutter_test as well.
-  analyzer: 0.27.4-alpha.14
+  analyzer: 0.27.4-alpha.15
 
 dev_dependencies:
   mockito: ^0.11.0