libevent: try optimizing for speed

This target comprises 1.17% of our total Chrome samples on CrOS, but
isn't optimized for speed. It may be worthwhile to optimize it in this
way.

Bug: 1143481
Change-Id: I9432b15330ab4fadf79a643a3abc54e8b59ed0a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2507829Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: George Burgess <gbiv@chromium.org>
Cr-Commit-Position: refs/heads/master@{#835347}

base/third_party/libevent/BUILD.gn

@@ -75,6 +75,11 @@ static_library("libevent") {
     include_dirs = [ "nacl_nonsfi" ]
   }
 
+  if (!is_debug) {
+    configs -= [ "//build/config/compiler:default_optimization" ]
+    configs += [ "//build/config/compiler:optimize_max" ]
+  }
+
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
 }