Our glReadPixels call (for canvas readback) uses GL_UNSIGNED_INT_8_8_8_8_REV. On iOS this is #defined to GL_RGBA, which is very wrong. We should use GL_UNSIGNED_BYTE.
Created attachment 221418 [details] Patch
<rdar://problem/15839956>
Committed r162160: <http://trac.webkit.org/changeset/162160>