There are a couple of bugs in the fast/canvas/webgl/gl-uniform-arrays.html that have been fixed in the Khronos WebGL conformance suite which should be brought into the WebKit copy of this test. One in particular is causing exceptions to be thrown when run in Chromium's DumpRenderTree, which causes test timeouts.
Created attachment 77252 [details] Patch
Committed r74499: <http://trac.webkit.org/changeset/74499>
http://trac.webkit.org/changeset/74743 might have broken GTK Linux 64-bit Debug