iOS: Add support for rendering native CVPixelBuffers directly

webrtc/sdk/objc/Framework/Classes/RTCShader+Private.h

+/*
+ *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#import "RTCShader.h"
+
+#import "WebRTC/RTCMacros.h"
+
+#if TARGET_OS_IPHONE
+#import <OpenGLES/ES3/gl.h>
+#else
+#import <OpenGL/gl3.h>
+#endif
+
+RTC_EXTERN const char kRTCVertexShaderSource[];
+
+RTC_EXTERN GLuint RTCCreateShader(GLenum type, const GLchar *source);
+RTC_EXTERN GLuint RTCCreateProgram(GLuint vertexShader, GLuint fragmentShader);
+RTC_EXTERN GLuint RTCCreateProgramFromFragmentSource(const char fragmentShaderSource[]);
+RTC_EXTERN BOOL RTCSetupVerticesForProgram(
+    GLuint program, GLuint* vertexBuffer, GLuint* vertexArray);