File Source/WebCore/platform/graphics/opengl/ExtensionsGLOpenGLES.cpp uses OpenGL ES 3 symbols glVertexAttribDivisor(), glDrawArraysInstanced(), and glDrawElementsInstanced(); and the GL_MAJOR_VERSION definition unconditionally without guarding the usage with HAVE(OPENGL_ES_3). This results in build failures with OpenGL ES driver headers which are strictly defining only ES2 symbols, and likely has been working most of the time because many drivers which also support ES3 (or the particular symbols used) included them when picking <GLES2/gl2.h> and/or <GLES/gl2ext.h>. One case in which build failures happen is the Mali driver provided by Buildroot's sunxi-mali-utgard package patches to allow using the Wayland variant with the following patch: https://o.perezdecastro.org/buildroot-sunxi-mali-utgard-wayland.diff Note that bug #255846 also needs solving to successfully compile WebKitGTK with the aforementioned Mali driver.
Pull request: https://github.com/WebKit/WebKit/pull/13084
Closing, the patch landed in the release branch long ago =)