Add basic shaders to Transformer

PiperOrigin-RevId: 393381694

library/transformer/src/main/assets/shaders/blit_vertex_shader.glsl

+// Copyright 2021 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+attribute vec4 a_position;
+attribute vec4 a_texcoord;
+uniform mat4 tex_transform;
+varying vec2 v_texcoord;
+void main() {
+  gl_Position = a_position;
+  v_texcoord = (tex_transform * a_texcoord).xy;
+}

library/transformer/src/main/assets/shaders/copy_external_fragment_shader.glsl

+// Copyright 2021 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#extension GL_OES_EGL_image_external : require
+precision mediump float;
+uniform samplerExternalOES tex_sampler;
+varying vec2 v_texcoord;
+void main() {
+  gl_FragColor = texture2D(tex_sampler, v_texcoord);
+}