Make popup menus line up to their baseline per the Material spec.

sky/sdk/lib/rendering/object.dart

Index: sky/sdk/lib/rendering/object.dart
diff --git a/sky/sdk/lib/rendering/object.dart b/sky/sdk/lib/rendering/object.dart
index 9624dc32ee022ec8246404ddd7c45fd39cbd9254..4898c79136fccc737662d1ae328194ed841162d9 100644
--- a/sky/sdk/lib/rendering/object.dart
+++ b/sky/sdk/lib/rendering/object.dart
@@ -70,7 +70,7 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
     assert(child != null);
     assert(child.parentData != null);
     child.parentData.detach();
-    child._cleanRelayoutSubtreeRoot();
+    child._maybeCleanParentDependencies();
     super.dropChild(child);
     markNeedsLayout();
   }
@@ -122,17 +122,27 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
       assert(parent == this.parent); // TODO(ianh): Remove this once the analyzer is cleverer
     } else {
       _nodesNeedingLayout.add(this);
-      scheduler.ensureVisualUpdate();
     }
   }
-  void _cleanRelayoutSubtreeRoot() {
-    if (_relayoutSubtreeRoot != this) {
-      _relayoutSubtreeRoot = null;
-      _needsLayout = true;
-      _cleanRelayoutSubtreeRootChildren();
-    }
+  static bool _debugCleaningParentDependencies = false;
+  bool _debugSetCleaningParentDependencies(bool value) {
+    _debugCleaningParentDependencies = value;
+    return true;
+  }
+  void _maybeCleanParentDependencies() {
+    assert(_debugSetCleaningParentDependencies(true));
+    if (_relayoutSubtreeRoot != this)
+      cleanParentDependencies();
+    assert(_debugSetCleaningParentDependencies(false));
   }
-  void _cleanRelayoutSubtreeRootChildren() { } // workaround for lack of inter-class mixins in Dart
+  void cleanParentDependencies() {
+    assert(_debugCleaningParentDependencies);
+    assert(_relayoutSubtreeRoot != this);
+    _relayoutSubtreeRoot = null;
+    _needsLayout = true;
+    _cleanParentDependenciesChildren();
+  }
+  void _cleanParentDependenciesChildren() { } // workaround for lack of inter-class mixins in Dart
   void scheduleInitialLayout() {
     assert(attached);
     assert(parent == null);
@@ -168,11 +178,12 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
       _debugDoingThisLayout = false;
       _debugCanParentUseSize = null;
     } catch (e, stack) {
-      print('Exception raised during layout of ${this}: ${e}');
+      print('Exception "${e}" raised during layout of:\n${this}');
       print(stack);
       return;
     }
     _needsLayout = false;
+    markNeedsPaint();
   }
   void layout(Constraints constraints, { bool parentUsesSize: false }) {
     final parent = this.parent; // TODO(ianh): Remove this once the analyzer is cleverer
@@ -217,7 +228,7 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
     //
     // When calling layout() on your children, pass in
     // "parentUsesSize: true" if your size or layout is dependent on
-    // your child's size.
+    // your child's size or intrinsic dimensions.
 
   // when the parent has rotated (e.g. when the screen has been turned
   // 90 degrees), immediately prior to layout() being called for the
@@ -329,9 +340,9 @@ abstract class RenderObjectWithChildMixin<ChildType extends RenderObject> implem
     if (_child != null)
       _child.detach();
   }
-  void _cleanRelayoutSubtreeRootChildren() {
+  void _cleanParentDependenciesChildren() {
     if (_child != null)
-      _child._cleanRelayoutSubtreeRoot();
+      _child._maybeCleanParentDependencies();
   }
   String debugDescribeChildren(String prefix) {
     if (child != null)
@@ -508,10 +519,10 @@ abstract class ContainerRenderObjectMixin<ChildType extends RenderObject, Parent
       child = child.parentData.nextSibling;
     }
   }
-  void _cleanRelayoutSubtreeRootChildren() {
+  void _cleanParentDependenciesChildren() {
     ChildType child = _firstChild;
     while (child != null) {
-      child._cleanRelayoutSubtreeRoot();
+      child._maybeCleanParentDependencies();
       assert(child.parentData is ParentDataType);
       child = child.parentData.nextSibling;
     }