Make mixed samples contingent on auxiliary extensions

include/gpu/gl/GrGLFunctions.h

Index: include/gpu/gl/GrGLFunctions.h
diff --git a/include/gpu/gl/GrGLFunctions.h b/include/gpu/gl/GrGLFunctions.h
index 5c2cf7bc4d12eac192fd7977ff42663e66f6faf1..cbab026968e980fac2a191ab42a5bcc12e35f6ef 100644
--- a/include/gpu/gl/GrGLFunctions.h
+++ b/include/gpu/gl/GrGLFunctions.h
@@ -164,6 +164,7 @@ extern "C" {
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLPopGroupMarkerProc)();
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLPushGroupMarkerProc)(GrGLsizei length, const char* marker);
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLQueryCounterProc)(GrGLuint id, GrGLenum target);
+    typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLRasterSamplesProc)(GrGLuint samples, GrGLboolean fixedsamplelocations);
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLReadBufferProc)(GrGLenum src);
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLReadPixelsProc)(GrGLint x, GrGLint y, GrGLsizei width, GrGLsizei height, GrGLenum format, GrGLenum type, GrGLvoid* pixels);
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLRenderbufferStorageProc)(GrGLenum target, GrGLenum internalformat, GrGLsizei width, GrGLsizei height);