Switch the Linux official build to PGO (from AFDO).

This switches the Linux official build from AFDO to PGO. This yield some
3-4% performance gains on Speedometer and help unifying our desktop
build configurations, PGO is already used on Win and Mac. The PGO
profiles for Linux are generated by a continuous bot and are rolled in
Chrome once or twice per day (AFDO is based on the Android profiles).

This increases binary size by ~3-4%.

Bug: 1111437
Change-Id: I565eb336fa5ad9480e99808ed49246634255b82d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2404620
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809040}

build/config/compiler/BUILD.gn

@@ -89,7 +89,7 @@ declare_args() {
   # nonsensical for said projects.
   clang_use_default_sample_profile =
       chrome_pgo_phase == 0 && build_with_chromium && is_official_build &&
-      (is_android || is_desktop_linux)
+      is_android
 
   # This configuration is used to select a default profile in Chrome OS based on
   # the microarchitectures we are using. This is only used if

build/config/compiler/pgo/pgo.gni

@@ -9,7 +9,7 @@ declare_args() {
   #     1 : Used during the PGI (instrumentation) phase.
   #     2 : Used during the PGO (optimization) phase.
   chrome_pgo_phase = 0
-  if (is_official_build && (is_win || is_mac)) {
+  if (is_official_build && (is_win || is_mac || (is_linux && !is_chromeos))) {
     chrome_pgo_phase = 2
   }