Revert "ipc: disable AFDO on Linux"

This reverts commit af31b7d.

The problem bit us again in crbug.com/1005023, so I implemented a more
general fix. As a result, we should now be safe to turn AFDO back on
here.

Bug: 916130
Change-Id: I0f29059f9eccaf62dfeeccf543a8cabbeeaf86a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1860881
Reviewed-by: Ken Rockot <rockot@google.com>
Commit-Queue: George Burgess <gbiv@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706266}

ipc/BUILD.gn

@@ -104,16 +104,6 @@ component("ipc") {
     "//base",
   ]
 
-  # TODO(https://crbug.com/916130): AFDO causes a substantial size increase in
-  # nacl_helper that originates from here. This is apparently due to some
-  # mixture of inlining, CFI, and (potentially) speculative devirtualization.
-  # Work around that by locally disabling AFDO.
-  #
-  # nacl_helper is only available on Linux.
-  if (is_linux) {
-    configs -= [ "//build/config/compiler:afdo" ]
-  }
-
   if (enable_ipc_fuzzer) {
     public_configs = [ "//tools/ipc_fuzzer:ipc_fuzzer_config" ]
   }