[Please, handle this bug with care, since it could be a Mesa regression. Reporting on KWin end]

When I run kwin_gles --replace &, I get the following output. 

OpenGL vendor string:                   X.Org
OpenGL renderer string:                 Gallium 0.4 on AMD PALM
OpenGL version string:                  OpenGL ES 3.0 Mesa 9.2.0
OpenGL shading language version string: OpenGL ES GLSL ES 3.0
Driver:                                 R600G
GPU class:                              EVERGREEN
OpenGL version:                         3.0
GLSL version:                           3.0
Mesa version:                           9.2
Linux kernel version:                   3.12
Direct rendering:                       yes
Requires strict binding:                no
GLSL shaders:                           yes
Texture NPOT support:                   yes
Virtual Machine:                        no
QCoreApplication::sendPostedEvents: Cannot send posted events for objects in another thread
QCoreApplication::sendPostedEvents: Cannot send posted events for objects in another thread
kwin(6551): Failed to compile fragment shader: 
"0:2(14): error: no precision specified this scope for type `vec4'
0:4(13): error: no precision specified this scope for type `float'
0:5(13): error: no precision specified this scope for type `float'
0:6(13): error: no precision specified this scope for type `float'
0:7(13): error: no precision specified this scope for type `float'
0:11(7): error: no precision specified this scope for type `vec4'

kwin(6551): Failed to link shader: 
"error: program lacks a fragment shader

This began to happen after the mesa-9.2-0.15.20130723.fc19 build, when Fedora released mesa 9.2. Before that, and even with mesa-9.2-0.15.20130723.fc19, kwin_gles worked properly (but without v-sync, because of a bug with Mesa).

As you can see, my setup is: AMD E-450 with Radeon 6320, kernel 3.12 rc1, free drivers and Mesa 9.2, with the Fedora patch set. Since I'm using the free driver, support should be good.

Reproducible: Always

Steps to Reproduce:
1. Enable Blur.
2. On a Radeon system with Mesa 9.2 release, run kwin_gles --replace &
3. See an output like mine.
Actual Results:  
Blur doesn't work. Everything else works properly.

Expected Results:  
Blur works.

kwin_gles only. kwin with KWIN_OPENGL_INTERFACE=egl does not exhibit this behavior.