/usr/include/OGRE/RenderSystems/GLES2/ is in libogre-1.9-dev 1.9.0+dfsg1-7.
This file is owned by root:root, with mode 0o755.
..
/usr/include/OGRE/RenderSystems/GLES2/GLES2/
/usr/include/OGRE/RenderSystems/GLES2/GLES2/gl2.h
/usr/include/OGRE/RenderSystems/GLES2/GLES2/gl2ext.h
/usr/include/OGRE/RenderSystems/GLES2/GLES2/gl2platform.h
/usr/include/OGRE/RenderSystems/GLES2/GLES2/gles2w.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESCgProgram.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESCgProgramFactory.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESExtSupport.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESGpuProgram.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESLinkProgram.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESLinkProgramManager.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESPreprocessor.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESProgram.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESProgramCommon.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESProgramFactory.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESProgramManagerCommon.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESProgramPipeline.h
/usr/include/OGRE/RenderSystems/GLES2/GLSLES/OgreGLSLESProgramPipelineManager.h
/usr/include/OGRE/RenderSystems/GLES2/KHR/
/usr/include/OGRE/RenderSystems/GLES2/KHR/khrplatform.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2Context.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2DefaultHardwareBufferManager.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2DepthBuffer.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2FBOMultiRenderTarget.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2FBORenderTexture.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2FrameBufferObject.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2GpuProgram.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2GpuProgramManager.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2HardwareBufferManager.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2HardwareIndexBuffer.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2HardwareOcclusionQuery.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2HardwarePixelBuffer.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2HardwareUniformBuffer.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2HardwareVertexBuffer.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2InternalShaders.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2ManagedResource.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2PixelFormat.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2Plugin.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2Prerequisites.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2RenderSystem.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2RenderTexture.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2RenderToVertexBuffer.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2StateCacheManager.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2Support.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2Texture.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2TextureManager.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2UniformCache.h
/usr/include/OGRE/RenderSystems/GLES2/OgreGLES2VertexDeclaration.h
/usr/include/OGRE/RenderSystems/GLES2/StateCacheManager/
/usr/include/OGRE/RenderSystems/GLES2/StateCacheManager/OgreGLES2NullStateCacheManagerImp.h
/usr/include/OGRE/RenderSystems/GLES2/StateCacheManager/OgreGLES2NullUniformCacheImp.h
/usr/include/OGRE/RenderSystems/GLES2/X11/
/usr/include/OGRE/RenderSystems/GLES2/X11/OgreEGLContext.h
/usr/include/OGRE/RenderSystems/GLES2/X11/OgreEGLRenderTexture.h
/usr/include/OGRE/RenderSystems/GLES2/X11/OgreEGLSupport.h
/usr/include/OGRE/RenderSystems/GLES2/X11/OgreEGLWindow.h
/usr/include/OGRE/RenderSystems/GLES2/X11/OgreGLES2Util.h
/usr/include/OGRE/RenderSystems/GLES2/X11/OgreX11EGLContext.h
/usr/include/OGRE/RenderSystems/GLES2/X11/OgreX11EGLRenderTexture.h
/usr/include/OGRE/RenderSystems/GLES2/X11/OgreX11EGLSupport.h
/usr/include/OGRE/RenderSystems/GLES2/X11/OgreX11EGLWindow.h