Fix texture buffer unbind and size query - Fixes a crash with glTexBuffer given 0 as buffer. - Fixes query of TEXTURE_BUFFER_SIZE. If glTexBuffer is used to bind a buffer, and the buffer is modified, the result of this query must adapt to the new buffer size. The spec mentions that unlike Desktop GL, ES doesn't have immutable buffers, and so they had no choice but to allow mutable buffers. Bug: angleproject:3573 Test: KHR-GLES31.core.texture_buffer.texture_buffer_parameters Test: dEQP-GLES31.functional.texture.texture_buffer.state_query.texture_buffer_size_integer Change-Id: Iec77c14ccf0e9ee11a171dbe2c7386678304bcc8 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2533494 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>