Please test also with Mesa master. For me this test passes on master with following configuration:

Haswell desktop
Chrome/45.0.2454.85
3.0 Mesa 11.1.0-devel (git-2832ca9)

I've upgraded Chrome to Chrome/46.0.2490.71 and now test fails. It uses following shader:

---8< ---
#version 130
out vec4 webgl_FragColor;
uniform sampler2D webgl_b10f4de6e0297af8[2];
float webgl_dc8ac432e5f2d0a5(in int webgl_4fc82888d13de398){
return (float(webgl_4fc82888d13de398) - float(webgl_4fc82888d13de398));
}
void main(){
vec4 webgl_95a61de88fbe7420 = vec4(0.0, 0.0, 0.0, 0.0);
for (int webgl_e8ffc6842a7e307d = 1; (webgl_e8ffc6842a7e307d < 3); (++webgl_e8ffc6842a7e307d))
{
if ((webgl_95a61de88fbe7420.x > 255.0))
{
(webgl_95a61de88fbe7420.x = (255.0 + webgl_dc8ac432e5f2d0a5(webgl_e8ffc6842a7e307d)));
break;
}
(webgl_95a61de88fbe7420 += texture(webgl_b10f4de6e0297af8[int(clamp(float((webgl_e8ffc6842a7e307d - 1)), 0.0, float(1)))], vec2(0.5, 0.5)));
}
(webgl_FragColor = webgl_95a61de88fbe7420);
}
--- 8< ---

Mesa correctly errors out with following error:

--- 8< ---
0:16(36): error: sampler arrays indexed with non-constant expressions are 
forbidden in GLSL 1.30 and later
--- 8< ---

This looks like a bug in Chrome, maybe the glsl translation/validation layer.

Confirmed with Mesa master #6f39546

Platform: SKY LAKE Y A0 
CPU : Intel(R) Core(TM) m5-6Y57 CPU @ 1.10GHz (family: 6, model: 78  stepping: 3)
MCP : SKL-Y  D1 2+2 (ou ULX-D1)
QDF : QJK9 
CPU : SKL D0
Chipset PCH: Sunrise Point LP C1       
CRB : SKY LAKE Y LPDDR3 RVP3 CRB FAB2
Reworks : All Mandatories + FBS02,FBS03, F23, O-02 & O-06
Software
BIOS : SKLSE2R1.R00.X097.B02.1509020030
ME FW : 11.0.0.1173
Ksc (EC FW): 1.19
Linux distribution: Ubuntu 14.04 LTS 64 bits
kernel 4.3.0-rc5-drm-intel-nightly+ (f14b17b) from git://anongit.freedesktop.org/drm-intel
commit f14b17b8639fb680c672d3d2f8d6414fcf0f82c4
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Fri Oct 16 19:27:49 2015 +0200
drm-intel-nightly: 2015y-10m-16d-17h-27m-10s UTC integration manifest
Mesa master commit 6f3954618b0fe273af76af79ce9ec56566b79b2a from http://cgit.freedesktop.org/mesa/mesa/
xf86-video-intel - 2.99.917 from http://cgit.freedesktop.org/xorg/driver/xf86-video-intel/
Libdrm - 2.4.65 from http://cgit.freedesktop.org/mesa/drm/
Libva - 1.6.1 from http://cgit.freedesktop.org/libva/
vaapi intel-driver - 1.6.1 from http://cgit.freedesktop.org/vaapi/intel-driver
Cairo - 1.14.2 from http://cgit.freedesktop.org/cairo
Xorg Xserver - 1.17.2 from http://cgit.freedesktop.org/xorg/xserver

For information it is Pass with Mesa 11.0.4 + kernel 4.3.0-rc6-drm-intel-nightly+ (ab48d30) from git://anongit.freedesktop.org/drm-intel

(In reply to cprigent from comment #4)
> For information it is Pass with Mesa 11.0.4 + kernel
> 4.3.0-rc6-drm-intel-nightly+ (ab48d30) from
> git://anongit.freedesktop.org/drm-intel

Can you please confirm which Chrome version is used when this is passing?

The test is passed with Chrome version is 45.0.2454.101 (64-bits). But when I upgraded Chrome to 46.0.2490.80 (64-bits), the test is failed.

(In reply to Olivier Berthier from comment #6)
> The test is passed with Chrome version is 45.0.2454.101 (64-bits). But when
> I upgraded Chrome to 46.0.2490.80 (64-bits), the test is failed.

We need a Chrome guy to investigate this. On Firefox and old Chrome this test passes fine, I don't believe this is a Mesa regression, also this is not specific to Skylake.

Dear Reporter,

This Mesa bug has been in the "NEEDINFO" status for over 60 days. I am closing this bug based on lack of response but feel free to reopen if resolution is still needed. Please ensure you're supplying the correct information as requested.

Thank you.