[Radar 28901861]
On macOS machines with an Intel Haswell GPU, when drawing to an FBO with a multisampled depth renderbuffer attached, some incorrect depth data will be written into the buffer if the buffer width falls into the ranges of [8N+4, 8N+8) where N>=0. 
This bug causes failures of fbomultisample.*_samples.html’s tests in the WebGL 2.0 conformance suite.
This bug does not occur on other GPU types on macOS, nor on other operating systems.


Steps to reproduce:

1. Download Chrome Canary and run from the Terminal:
/Applications/Google\ Chrome\ Canary.app/Contents/MacOS/Google\ Chrome\ Canary --enable-unsafe-es3-apis

2. Check out the KhronosGroup/WebGL repository:
git clone https://github.com/KhronosGroup/WebGL.git

3. Launch an HTTP server against that repository:
cd WebGL
python -m SimpleHTTPServer

4. Navigate the browser to the test cases:
http://localhost:8000/sdk/tests/deqp/functional/gles3/fbomultisample.8_samples.html?webglVersion=2&quiet=0
http://localhost:8000/sdk/tests/deqp/functional/gles3/fbomultisample.4_samples.html?webglVersion=2&quiet=0
http://localhost:8000/sdk/tests/deqp/functional/gles3/fbomultisample.2_samples.html?webglVersion=2&quiet=0

These tests are also available online at:
http://www.khronos.org/registry/webgl/sdk/tests/deqp/functional/gles3/fbomultisample.8_samples.html?webglVersion=2&quiet=0
http://www.khronos.org/registry/webgl/sdk/tests/deqp/functional/gles3/fbomultisample.4_samples.html?webglVersion=2&quiet=0
http://www.khronos.org/registry/webgl/sdk/tests/deqp/functional/gles3/fbomultisample.2_samples.html?webglVersion=2&quiet=0


Expected Results:

Expect all tests to pass, as they do on other operating systems and on other GPU types on macOS.


Actual Results:

The test cases involving renderbuffers of any depth format fail.


OS X Build/Version:

macOS Sierra (10.12)
MacBook Pro-Mid 2015-Intel Iris Pro Graphics 5200 

Notes:

NOT reproducible on MacBook-Early 2016-Intel HD Graphics 515