Remove unused examples targets. (flutter/engine#6882)

These target are no longer built or referenced in either the Flutter or
Fuchsia buildroots. Similar examples are present in the examples/ directory
in the framework.

engine/src/flutter/examples/BUILD.gn

@@ -1,11 +0,0 @@
-# Copyright 2013 The Flutter Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-group("examples") {
-  deps = [
-    "hello_flutter",
-    "hello_flutter:hello_flutter_aot",
-    "spinning_square",
-  ]
-}

engine/src/flutter/examples/hello_flutter/lib/main.dart

@@ -1,50 +0,0 @@
-// Copyright 2013 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// This example shows how to show the text 'Hello, world.' using the raw
-// interface to the engine.
-
-import 'dart:ui' as ui;
-
-void beginFrame(Duration timeStamp) {
-  final double devicePixelRatio = ui.window.devicePixelRatio;
-  final ui.Size physicalSize = ui.window.physicalSize;
-  final ui.Size logicalSize = physicalSize / devicePixelRatio;
-
-  final ui.ParagraphBuilder paragraphBuilder = new ui.ParagraphBuilder(new ui.ParagraphStyle())
-    ..addText('Hello, world.');
-  final ui.Paragraph paragraph = paragraphBuilder.build()
-    ..layout(new ui.ParagraphConstraints(width: logicalSize.width));
-
-  final ui.Rect physicalBounds = ui.Offset.zero & physicalSize;
-  final ui.PictureRecorder recorder = new ui.PictureRecorder();
-  final ui.Canvas canvas = new ui.Canvas(recorder, physicalBounds);
-  canvas.scale(devicePixelRatio, devicePixelRatio);
-  canvas.drawRect(ui.Offset.zero & logicalSize, new ui.Paint()..color = const ui.Color(0xFF0000FF));
-  canvas.drawParagraph(paragraph, new ui.Offset(
-    (logicalSize.width - paragraph.maxIntrinsicWidth) / 2.0,
-    (logicalSize.height - paragraph.height) / 2.0
-  ));
-  final ui.Picture picture = recorder.endRecording();
-
-  final ui.SceneBuilder sceneBuilder = new ui.SceneBuilder()
-    // TODO(abarth): We should be able to add a picture without pushing a
-    // container layer first.
-    ..pushClipRect(physicalBounds)
-    ..addPicture(ui.Offset.zero, picture)
-    ..pop();
-
-  ui.window.render(sceneBuilder.build());
-}
-
-// This function is the primary entry point to your application. The engine
-// calls main() as soon as it has loaded your code.
-void main() {
-  // The engine calls onBeginFrame whenever it wants us to produce a frame.
-  ui.window.onBeginFrame = beginFrame;
-  // Here we kick off the whole process by asking the engine to schedule a new
-  // frame. The engine will eventually call onBeginFrame when it is time for us
-  // to actually produce the frame.
-  ui.window.scheduleFrame();
-}

engine/src/flutter/examples/hello_flutter/pubspec.yaml

@@ -1,3 +0,0 @@
-# Copyright 2013 The Flutter Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.

engine/src/flutter/examples/spinning_square/lib/main.dart

@@ -1,60 +0,0 @@
-// Copyright 2013 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// This example shows how to perform a simple animation using the raw interface
-// to the engine.
-
-import 'dart:math' as math;
-import 'dart:typed_data';
-import 'dart:ui' as ui;
-
-void beginFrame(Duration timeStamp) {
-  // The timeStamp argument to beginFrame indicates the timing information we
-  // should use to clock our animations. It's important to use timeStamp rather
-  // than reading the system time because we want all the parts of the system to
-  // coordinate the timings of their animations. If each component read the
-  // system clock independently, the animations that we processed later would be
-  // slightly ahead of the animations we processed earlier.
-
-  final double devicePixelRatio = ui.window.devicePixelRatio;
-
-  // PAINT
-  final ui.Size logicalSize = ui.window.physicalSize / devicePixelRatio;
-  final ui.Rect paintBounds = ui.Offset.zero & logicalSize;
-  final ui.PictureRecorder recorder = new ui.PictureRecorder();
-  final ui.Canvas canvas = new ui.Canvas(recorder, paintBounds);
-  canvas.translate(paintBounds.width / 2.0, paintBounds.height / 2.0);
-
-  // Here we determine the rotation according to the timeStamp given to us by
-  // the engine.
-  final double t = timeStamp.inMicroseconds / Duration.MICROSECONDS_PER_MILLISECOND / 1800.0;
-  canvas.rotate(math.PI * (t % 1.0));
-
-  canvas.drawRect(new ui.Rect.fromLTRB(-100.0, -100.0, 100.0, 100.0),
-                  new ui.Paint()..color = const ui.Color.fromARGB(255, 0, 255, 0));
-  final ui.Picture picture = recorder.endRecording();
-
-  // COMPOSITE
-
-  final Float64List deviceTransform = new Float64List(16)
-    ..[0] = devicePixelRatio
-    ..[5] = devicePixelRatio
-    ..[10] = 1.0
-    ..[15] = 1.0;
-  final ui.SceneBuilder sceneBuilder = new ui.SceneBuilder()
-    ..pushTransform(deviceTransform)
-    ..addPicture(ui.Offset.zero, picture)
-    ..pop();
-  ui.window.render(sceneBuilder.build());
-
-  // After rendering the current frame of the animation, we ask the engine to
-  // schedule another frame. The engine will call beginFrame again when its time
-  // to produce the next frame.
-  ui.window.scheduleFrame();
-}
-
-void main() {
-  ui.window.onBeginFrame = beginFrame;
-  ui.window.scheduleFrame();
-}

engine/src/flutter/examples/spinning_square/pubspec.yaml

@@ -1,3 +0,0 @@
-# Copyright 2013 The Flutter Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.