So ANGLE seems to have a bug in this then

Qiankun would you like to try solving the ANGLE bug? You should start by porting the WebGL test to an angle_end2end_test in FramebufferTest.cpp.

This is not a bug of ANGLE. It's a driver bug. The FRAMEBUFFER_UNSUPPORT status comes from a driver call  "GLenum status = mFunctions->checkFramebufferStatus(GL_FRAMEBUFFER);" in angle/src/libANGLE/renderer/gl/FramebufferGL.cpp::FramebufferGL::checkStatus(), see https://cs.chromium.org/chromium/src/third_party/angle/src/libANGLE/renderer/gl/FramebufferGL.cpp?rcl=0&l=373.

I ported the test to ANGLE: https://chromium-review.googlesource.com/#/c/426007/.

The following revision refers to this bug:
  https://chromium.googlesource.com/angle/angle/+/b293a2601d29a95c0716725e460b395fff29e8e5

commit b293a2601d29a95c0716725e460b395fff29e8e5
Author: Qiankun Miao <qiankun.miao@intel.com>
Date: Mon Jan 09 04:35:36 2017

Fbo attaching non-zero base level texture should be complete

This is ported from WebGL CTS which is used to verify a ES 3.0 bug in
NVIDIA Linux, Windows OpenGL, and Mac OSX.

BUG=chromium:678526
TEST=angle_end2end_tests

Change-Id: Ifb6e1ba52d45144c544beab21f1ad4a98b1b0f65
Reviewed-on: https://chromium-review.googlesource.com/426007
Commit-Queue: Qiankun Miao <qiankun.miao@intel.com>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>

[modify] https://crrev.com/b293a2601d29a95c0716725e460b395fff29e8e5/src/tests/gl_tests/FramebufferTest.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/806ee17727dce5a50eff16b2010b4189751370cd

commit 806ee17727dce5a50eff16b2010b4189751370cd
Author: geofflang <geofflang@chromium.org>
Date: Tue Jan 10 23:00:12 2017

Roll ANGLE 037340d..98e3407

https://chromium.googlesource.com/angle/angle.git/+log/037340d..98e3407

BUG=chromium:678526, chromium:679607 ,chromium:679725

TBR=jmadill@chromium.org

TEST=bots

CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2623983002
Cr-Commit-Position: refs/heads/master@{#442718}

[modify] https://crrev.com/806ee17727dce5a50eff16b2010b4189751370cd/DEPS

 Issue 680278  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/60a0ea7031403c2cb2d2cd4b27aa1be9932154a7

commit 60a0ea7031403c2cb2d2cd4b27aa1be9932154a7
Author: zmo <zmo@chromium.org>
Date: Thu Feb 16 01:23:31 2017

Update WebGL2 conformance test expectations after roll.

The expectation change is caused by https://github.com/KhronosGroup/WebGL/pull/2289

BUG=678526
TEST=Linux NVidia bot on FYI waterfall
TBR=kbr@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2693213004
Cr-Commit-Position: refs/heads/master@{#450853}

[modify] https://crrev.com/60a0ea7031403c2cb2d2cd4b27aa1be9932154a7/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

unassigned me. I may not have time to investigate this in short term. 

Jiajia Qin will take over this issue.

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Jiajia / Yang: Could you please look into whether this issue is still present, and whether we should still fix it?

Hi Kai. This issue still exists on Intel Mac. I have filed bug to our driver team. I will update the status once the bug is fixed.

Sorry, I should send a radar description for Mac issue.
Kai/kbr, I put the radar description here https://docs.google.com/document/d/1Uq2eYUIVy_llwkcfs3GLFVLNMDvWv2sNUiG0RT66pig/edit?ts=5b052ae5. Please take a look, thanks. 

Sorry for the delay. I just posted the radar: 40656957.

Thanks Jiajia for writing up the Radar and Kai for filing it.

Kai, if you could ping Apple telling them about it, and add it to our shared spreadsheet, that would be helpful. Thanks again.

We need to fix or workaround this for conformance. conformance2/rendering/framebuffer-texture-level1.html is the failing test.