I noticed some of the demos don't include precision qualifiers in their fragment shaders. These shaders fail to compile on an OpenGL ES 2.0 conformant implementation.
These shaders require either explicit precision qualifiers on their variables, or a global default precision specifier. Note: highp is not mandated in fragment shaders, but is available through an OpenGL ES 2.0 extension.
Someone was messing with Bugzilla today. Assigning back to WebGL.