Gate the PhysicalModel shadows behind a flag (#9198)

Fixes https://github.com/flutter/flutter/issues/9186

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

@@ -7,6 +7,7 @@ import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 
 import 'constants.dart';
+import 'shadows.dart';
 import 'theme.dart';
 
 /// Signature for the callback used by ink effects to obtain the rectangle for the effect.
@@ -187,6 +188,9 @@ class Material extends StatefulWidget {
 
   /// The default radius of an ink splash in logical pixels.
   static const double defaultSplashRadius = 35.0;
+
+  // Temporary flag used to enable the PhysicalModel shadow implementation.
+  static bool debugEnablePhysicalModel = false;
 }
 
 class _MaterialState extends State<Material> with TickerProviderStateMixin {
@@ -232,30 +236,41 @@ class _MaterialState extends State<Material> with TickerProviderStateMixin {
       )
     );
 
-    if (config.type == MaterialType.circle) {
-      contents = new PhysicalModel(
-        shape: BoxShape.circle,
-        elevation: config.elevation,
-        color: backgroundColor,
-        child: contents,
-      );
-    } else if (config.type == MaterialType.transparency) {
-      if (radius == null) {
-        contents = new ClipRect(child: contents);
+    if (Material.debugEnablePhysicalModel) {
+      if (config.type == MaterialType.circle) {
+        contents = new PhysicalModel(
+          shape: BoxShape.circle,
+          elevation: config.elevation,
+          color: backgroundColor,
+          child: contents,
+        );
+      } else if (config.type == MaterialType.transparency) {
+        if (radius == null) {
+          contents = new ClipRect(child: contents);
+        } else {
+          contents = new ClipRRect(
+            borderRadius: radius,
+            child: contents
+          );
+        }
       } else {
+        contents = new PhysicalModel(
+          shape: BoxShape.rectangle,
+          borderRadius: radius ?? BorderRadius.zero,
+          elevation: config.elevation,
+          color: backgroundColor,
+          child: contents,
+        );
+      }
+    } else {
+      if (config.type == MaterialType.circle) {
+        contents = new ClipOval(child: contents);
+      } else if (kMaterialEdges[config.type] != null) {
         contents = new ClipRRect(
           borderRadius: radius,
           child: contents
         );
       }
-    } else {
-      contents = new PhysicalModel(
-        shape: BoxShape.rectangle,
-        borderRadius: radius ?? BorderRadius.zero,
-        elevation: config.elevation,
-        color: backgroundColor,
-        child: contents,
-      );
     }
 
     if (config.type != MaterialType.transparency) {
@@ -264,6 +279,8 @@ class _MaterialState extends State<Material> with TickerProviderStateMixin {
         duration: kThemeChangeDuration,
         decoration: new BoxDecoration(
           borderRadius: radius,
+          boxShadow: config.elevation == 0 || Material.debugEnablePhysicalModel ?
+              null : kElevationToShadow[config.elevation],
           shape: config.type == MaterialType.circle ? BoxShape.circle : BoxShape.rectangle
         ),
         child: new Container(

packages/flutter/test/material/ink_paint_test.dart

@@ -9,6 +9,8 @@ import 'package:flutter_test/flutter_test.dart';
 import '../rendering/mock_canvas.dart';
 
 void main() {
+  Material.debugEnablePhysicalModel = true;
+
   testWidgets('Does the ink widget render a border radius', (WidgetTester tester) async {
     final Color highlightColor = new Color(0xAAFF0000);
     final Color splashColor = new Color(0xAA0000FF);