BoxDecoration API changes: backgroundColor -> color et al (#9648)

backgroundColor -> color
backgroundImage -> image
BackgroundImage -> DecorationImage

examples/layers/widgets/media_query.dart

diff --git a/examples/layers/widgets/media_query.dart b/examples/layers/widgets/media_query.dart
index d7aec23..d96017e 100644
--- a/examples/layers/widgets/media_query.dart
+++ b/examples/layers/widgets/media_query.dart
@@ -17,9 +17,7 @@
           width: 32.0,
           height: 32.0,
           margin: const EdgeInsets.all(8.0),
-          decoration: new BoxDecoration(
-            backgroundColor: Colors.lightBlueAccent.shade100
-          )
+          color: Colors.lightBlueAccent.shade100,
         ),
         new Text(name)
       ]
@@ -39,9 +37,7 @@
         children: <Widget>[
           new Expanded(
             child: new Container(
-              decoration: new BoxDecoration(
-                backgroundColor: Colors.lightBlueAccent.shade100
-              )
+              color: Colors.lightBlueAccent.shade100,
             )
           ),
           new Container(

examples/layers/widgets/spinning_mixed.dart

diff --git a/examples/layers/widgets/spinning_mixed.dart b/examples/layers/widgets/spinning_mixed.dart
index 2a1c06d..71ba4da 100644
--- a/examples/layers/widgets/spinning_mixed.dart
+++ b/examples/layers/widgets/spinning_mixed.dart
@@ -25,7 +25,7 @@
   Widget build(BuildContext context) {
     return new Expanded(
       child: new Container(
-        decoration: new BoxDecoration(backgroundColor: color)
+        color: color,
       )
     );
   }

examples/layers/widgets/spinning_square.dart

diff --git a/examples/layers/widgets/spinning_square.dart b/examples/layers/widgets/spinning_square.dart
index e9a4f7b..be59f1c 100644
--- a/examples/layers/widgets/spinning_square.dart
+++ b/examples/layers/widgets/spinning_square.dart
@@ -37,9 +37,7 @@
       child: new Container(
         width: 200.0,
         height: 200.0,
-        decoration: const BoxDecoration(
-          backgroundColor: const Color(0xFF00FF00)
-        )
+        color: const Color(0xFF00FF00),
       )
     );
   }