Temporarily remove screenshot service extension that is causing code size issues (#21749)

* Revert "Avoid ever creating the WidgetInspectorService outside of debug mode. (#21648)"

This reverts commit eeebd833.

* Remove inspector screenshot service extension.

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

@@ -293,7 +293,6 @@ abstract class WidgetsBinding extends BindingBase with SchedulerBinding, Gesture
       }
     );
 
-    assert(() {
     // This service extension is deprecated and will be removed by 7/1/2018.
     // Use ext.flutter.inspector.show instead.
     registerBoolServiceExtension(
@@ -308,8 +307,6 @@ abstract class WidgetsBinding extends BindingBase with SchedulerBinding, Gesture
     );
 
     WidgetInspectorService.instance.initServiceExtensions(registerServiceExtension);
-      return true;
-    }());
   }
 
   Future<Null> _forceRebuild() {

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

@@ -13,7 +13,6 @@ import 'dart:ui' as ui
         window,
         ClipOp,
         Image,
-        ImageByteFormat,
         Paragraph,
         Picture,
         PictureRecorder,
@@ -1027,33 +1026,6 @@ class WidgetInspectorService {
       name: 'isWidgetCreationTracked',
       callback: isWidgetCreationTracked,
     );
-    registerServiceExtension(
-      name: 'screenshot',
-      callback: (Map<String, String> parameters) async {
-        assert(parameters.containsKey('id'));
-        assert(parameters.containsKey('width'));
-        assert(parameters.containsKey('height'));
-
-        final ui.Image image = await screenshot(
-          toObject(parameters['id']),
-          width: double.parse(parameters['width']),
-          height: double.parse(parameters['height']),
-          margin: parameters.containsKey('margin') ?
-              double.parse(parameters['margin']) : 0.0,
-          maxPixelRatio: parameters.containsKey('maxPixelRatio') ?
-              double.parse(parameters['maxPixelRatio']) : 1.0,
-          debugPaint: parameters['debugPaint'] == 'true',
-        );
-        if (image == null) {
-          return <String, Object>{'result': null};
-        }
-        final ByteData byteData = await image.toByteData(format:ui.ImageByteFormat.png);
-
-        return <String, Object>{
-          'result': base64.encoder.convert(Uint8List.view(byteData.buffer)),
-        };
-      },
-    );
   }
 
   /// Clear all InspectorService object references.

packages/flutter/test/foundation/service_extensions_test.dart

@@ -512,7 +512,7 @@ void main() {
 
     // If you add a service extension... TEST IT! :-)
     // ...then increment this number.
-    expect(binding.extensions.length, 38);
+    expect(binding.extensions.length, 37);
 
     expect(console, isEmpty);
     debugPrint = debugPrintThrottled;