[rename fixit] MultiChildLayoutDelegate#isChild -> hasChild

Fixes #459

packages/flutter/lib/src/material/scaffold.dart

@@ -51,12 +51,12 @@ class _ScaffoldLayout extends MultiChildLayoutDelegate {
     double contentTop = padding.top;
     double contentBottom = size.height - padding.bottom;
 
-    if (isChild(_ScaffoldSlot.toolBar)) {
+    if (hasChild(_ScaffoldSlot.toolBar)) {
       contentTop = layoutChild(_ScaffoldSlot.toolBar, fullWidthConstraints).height;
       positionChild(_ScaffoldSlot.toolBar, Offset.zero);
     }
 
-    if (isChild(_ScaffoldSlot.body)) {
+    if (hasChild(_ScaffoldSlot.body)) {
       final double bodyHeight = contentBottom - contentTop;
       final BoxConstraints bodyConstraints = fullWidthConstraints.tighten(height: bodyHeight);
       layoutChild(_ScaffoldSlot.body, bodyConstraints);
@@ -75,17 +75,17 @@ class _ScaffoldLayout extends MultiChildLayoutDelegate {
     Size bottomSheetSize = Size.zero;
     Size snackBarSize = Size.zero;
 
-    if (isChild(_ScaffoldSlot.bottomSheet)) {
+    if (hasChild(_ScaffoldSlot.bottomSheet)) {
       bottomSheetSize = layoutChild(_ScaffoldSlot.bottomSheet, fullWidthConstraints);
       positionChild(_ScaffoldSlot.bottomSheet, new Offset((size.width - bottomSheetSize.width) / 2.0, contentBottom - bottomSheetSize.height));
     }
 
-    if (isChild(_ScaffoldSlot.snackBar)) {
+    if (hasChild(_ScaffoldSlot.snackBar)) {
       snackBarSize = layoutChild(_ScaffoldSlot.snackBar, fullWidthConstraints);
       positionChild(_ScaffoldSlot.snackBar, new Offset(0.0, contentBottom - snackBarSize.height));
     }
 
-    if (isChild(_ScaffoldSlot.floatingActionButton)) {
+    if (hasChild(_ScaffoldSlot.floatingActionButton)) {
       final Size fabSize = layoutChild(_ScaffoldSlot.floatingActionButton, looseConstraints);
       final double fabX = size.width - fabSize.width - _kFloatingActionButtonMargin;
       double fabY = contentBottom - fabSize.height - _kFloatingActionButtonMargin;
@@ -96,7 +96,7 @@ class _ScaffoldLayout extends MultiChildLayoutDelegate {
       positionChild(_ScaffoldSlot.floatingActionButton, new Offset(fabX, fabY));
     }
 
-    if (isChild(_ScaffoldSlot.drawer)) {
+    if (hasChild(_ScaffoldSlot.drawer)) {
       layoutChild(_ScaffoldSlot.drawer, new BoxConstraints.tight(size));
       positionChild(_ScaffoldSlot.drawer, Offset.zero);
     }

packages/flutter/lib/src/rendering/custom_layout.dart

@@ -32,7 +32,7 @@ abstract class MultiChildLayoutDelegate {
   /// Call this from the [performLayout] or [getSize] methods to
   /// determine which children are available, if the child list might
   /// vary.
-  bool isChild(Object childId) => _idToChild[childId] != null;
+  bool hasChild(Object childId) => _idToChild[childId] != null;
 
   /// Ask the child to update its layout within the limits specified by
   /// the constraints parameter. The child's size is returned.

packages/flutter/test/widget/custom_multi_child_layout_test.dart

@@ -28,7 +28,7 @@ class TestMultiChildLayoutDelegate extends MultiChildLayoutDelegate {
       BoxConstraints constraints = new BoxConstraints.loose(size);
       performLayoutSize0 = layoutChild(0, constraints);
       performLayoutSize1 = layoutChild(1, constraints);
-      performLayoutIsChild = isChild('fred');
+      performLayoutIsChild = hasChild('fred');
     }, returnsNormally);
   }