Make comment about symbol_level=2 explicit that it slows compile

build/config/compiler/compiler.gni

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/compiler/pgo/pgo.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/goma.gni")
@@ skipping 83 matching lines @@
     symbol_level = 1
   } else if (is_win && use_goma && !is_clang) {
     # goma doesn't support PDB files, so we disable symbols during goma
     # compilation because otherwise the redundant debug information generated
     # by visual studio (repeated in every .obj file) makes linker
     # memory consumption and link times unsustainable (crbug.com/630074).
     # Clang on windows does not have this issue.
     symbol_level = 1
   } else if ((!is_nacl && !is_linux) || is_debug || is_official_build ||
              is_chromecast) {
-    # Linux is slowed by having symbols as part of the target binary, whereas
-    # Mac and Windows have them separate, so in Release Linux, default them off,
-    # but keep them on for Official builds and Chromecast builds.
+    # Linux builds slower by having symbols as part of the target binary,
+    # whereas Mac and Windows have them separate, so in Release Linux, default
+    # them off, but keep them on for Official builds and Chromecast builds.
     symbol_level = 2
   } else if (using_sanitizer) {
     # Sanitizers require symbols for filename suppressions to work.
     symbol_level = 1
   } else {
     symbol_level = 0
   }
 }
 
 # Assert that the configuration isn't going to hit https://crbug.com/648948.
 assert(ignore_elf32_limitations || !is_android ||
            (android_64bit_target_cpu && !build_apk_secondary_abi) ||
            is_component_build || symbol_level < 2,
        "Android 32-bit non-component, non-clang builds cannot have " +
            "symbol_level=2 due to 4GiB file size limit, see " +
            "https://crbug.com/648948. If you really want to try this out, " +
            "set ignore_elf32_limitations=true.")