Revert of Add support for glMapBufferRange. Use glMapBufferRange and glMapBufferSubData.

src/gpu/gl/GrGLAssembleInterface.cpp

Index: src/gpu/gl/GrGLAssembleInterface.cpp
diff --git a/src/gpu/gl/GrGLAssembleInterface.cpp b/src/gpu/gl/GrGLAssembleInterface.cpp
index e4337259a22de23161fc1b6fd228e0ac1b97defd..aed11e539f74d70674c2830827522f3f50f570af 100644
--- a/src/gpu/gl/GrGLAssembleInterface.cpp
+++ b/src/gpu/gl/GrGLAssembleInterface.cpp
@@ -171,11 +171,6 @@
         GET_PROC(BindVertexArray);
         GET_PROC(GenVertexArrays);
         GET_PROC(DeleteVertexArrays);
-    }
-
-    if (glVer >= GR_GL_VER(3,0) || extensions.has("GL_ARB_map_buffer_range")) {
-        GET_PROC(MapBufferRange);
-        GET_PROC(FlushMappedBufferRange);
     }
 
     // First look for GL3.0 FBO or GL_ARB_framebuffer_object (same since