NV_read_{depth,depth_stencil} is not available in unextended ES3.

src/Context.cpp

@@ -231,7 +231,9 @@ const std::vector<Extension>& Extension::extensions(Version version) {
         _extension(GL,EXT,robustness),
         _extension(GL,KHR,debug),
         _extension(GL,NV,read_buffer_front),
+        _extension(GL,NV,read_depth),
         _extension(GL,NV,read_stencil),
+        _extension(GL,NV,read_depth_stencil),
         _extension(GL,NV,texture_border_clamp),             // done
         _extension(GL,OES,depth32),
         _extension(GL,OES,mapbuffer),
@@ -254,8 +256,6 @@ const std::vector<Extension>& Extension::extensions(Version version) {
         _extension(GL,NV,draw_buffers),
         _extension(GL,NV,fbo_color_attachments),
         _extension(GL,NV,read_buffer),
-        _extension(GL,NV,read_depth),
-        _extension(GL,NV,read_depth_stencil),
         _extension(GL,NV,framebuffer_blit),                 // done
         _extension(GL,NV,framebuffer_multisample),
         _extension(GL,OES,depth24),

src/Extensions.h

@@ -235,9 +235,9 @@ namespace GL {
         _extension(GL,NV,fbo_color_attachments,     GLES200, GLES300) // #92
         _extension(GL,NV,read_buffer,               GLES200, GLES300) // #93
         _extension(GL,NV,read_buffer_front,         GLES200,    None) // #93
-        _extension(GL,NV,read_depth,                GLES200, GLES300) // #94
+        _extension(GL,NV,read_depth,                GLES200,    None) // #94
         _extension(GL,NV,read_stencil,              GLES200,    None) // #94
-        _extension(GL,NV,read_depth_stencil,        GLES200, GLES300) // #94
+        _extension(GL,NV,read_depth_stencil,        GLES200,    None) // #94
         _extension(GL,NV,framebuffer_blit,          GLES200, GLES300) // #142
         _extension(GL,NV,framebuffer_multisample,   GLES200, GLES300) // #143
         _extension(GL,NV,texture_border_clamp,      GLES200,    None) // #149