Revert "Implemented a CallDAG to allow for more AST analysis" failures in angle_unittests and compilation failure on clang (see: https://build.chromium.org/p/chromium.gpu.fyi/builders/GPU%20Mac%20Builder%20%28dbg%29/builds/30016/steps/compile/logs/stdio) . This reverts commit b34d1d12969496b1b0fb53934b8ce3200304f900. Change-Id: Ia995fb2db0e891294f3461de01617cb13e5ae381 Reviewed-on: https://chromium-review.googlesource.com/263727 Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>