iOS render: Handle frame rotation in OpenGL

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);
+RTC_EXTERN void RTCSetVertexData(int rotation);