--- a/build/config/compiler/BUILD.gn	2018-09-27 17:46:15.466610575 
-0400
+++ b/build/config/compiler/BUILD.gn.new	2018-09-27 
17:47:08.756982567 -0400
@@ -235,8 +235,6 @@
 
   configs += [
     # See the definitions below.
-    ":clang_revision",
-    ":compiler_cpu_abi",
     ":compiler_codegen",
   ]
 
@@ -501,17 +499,6 @@
     }
   }
 
-  if (is_clang && !is_nacl && !use_xcode_clang) {
-    cflags += [
-      # TODO(hans): Remove this once Clang generates better optimized debug info
-      # by default. https://crbug.com/765793
-      "-Xclang",
-      "-mllvm",
-      "-Xclang",
-      "-instcombine-lower-dbg-declare=0",
-    ]
-  }
-
   # Print absolute paths in diagnostics. There is no precedent for doing this
   # on Linux/Mac (GCC doesn't support it), but MSVC does this with /FC and
   # Windows developers rely on it (crbug.com/636109) so only do this on Windows.
@@ -1476,14 +1476,9 @@
         # Flags NaCl (Clang 3.7) and Xcode 9.2 (Clang clang-900.0.39.2) do not
         # recognize.
         cflags += [
-          # Ignore warnings about MSVC optimization pragmas.
-          # TODO(thakis): Only for no_chromium_code? http://crbug.com/505314
-          "-Wno-ignored-pragma-optimize",
         ]
         if (is_fuchsia) {
           cflags += [
-            # TODO(hans): https://crbug.com/890307
-            "-Wno-defaulted-function-deleted",
           ]
         }
       }
@@ -1545,22 +1526,6 @@
       "__STDC_FORMAT_MACROS",
     ]
 
-    if (!is_debug && !using_sanitizer &&
-        (!is_linux || !is_clang || is_official_build) &&
-        current_cpu != "s390x" && current_cpu != "s390" &&
-        current_cpu != "ppc64" && current_cpu != "ppc64" &&
-        current_cpu != "mips" && current_cpu != "mips64") {
-      # _FORTIFY_SOURCE isn't really supported by Clang now, see
-      # http://llvm.org/bugs/show_bug.cgi?id=16821.
-      # It seems to work fine with Ubuntu 12 headers though, so use it in
-      # official builds.
-      #
-      # Non-chromium code is not guaranteed to compile cleanly with
-      # _FORTIFY_SOURCE. Also, fortified build may fail when optimizations are
-      # disabled, so only do that for Release build.
-      defines += [ "_FORTIFY_SOURCE=2" ]
-    }
-
     if (is_mac) {
       cflags_objc = [ "-Wobjc-missing-property-synthesis" ]
       cflags_objcc = [ "-Wobjc-missing-property-synthesis" ]
@@ -1930,7 +1895,8 @@
 }
 
 # Default "optimization on" config.
-config("optimize") {
+config("optimize") { }
+config("xoptimize") {
   if (is_win) {
     # TODO(thakis): Remove is_clang here, https://crbug.com/598772
     if (is_official_build && full_wpo_on_official && !is_clang) {
@@ -1964,7 +1930,8 @@
 }
 
 # Same config as 'optimize' but without the WPO flag.
-config("optimize_no_wpo") {
+config("optimize_no_wpo") { }
+config("xoptimize_no_wpo") {
   if (is_win) {
     # Favor size over speed, /O1 must be before the common flags. The GYP
     # build also specifies /Os and /GF but these are implied by /O1.
@@ -1987,7 +1954,8 @@
 }
 
 # Turn off optimizations.
-config("no_optimize") {
+config("no_optimize") { }
+config("xno_optimize") {
   if (is_win) {
     cflags = [
       "/Od",  # Disable optimization.
@@ -2011,7 +1979,8 @@
 # Turns up the optimization level. On Windows, this implies whole program
 # optimization and link-time code generation which is very expensive and should
 # be used sparingly.
-config("optimize_max") {
+config("optimize_max") { }
+config("xoptimize_max") {
   if (is_nacl && is_nacl_irt) {
     # The NaCl IRT is a special case and always wants its own config.
     # Various components do:
@@ -2062,7 +2031,8 @@
 #
 # TODO(crbug.com/621335) - rework how all of these configs are related
 # so that we don't need this disclaimer.
-config("optimize_speed") {
+config("optimize_speed") { }
+config("xoptimize_speed") {
   if (is_nacl && is_nacl_irt) {
     # The NaCl IRT is a special case and always wants its own config.
     # Various components do:
@@@ -2067,7 +2067,8 @@
   }
 }
 
-config("optimize_fuzzing") {
+config("optimize_fuzzing") { }
+config("xoptimize_fuzzing") {
   cflags = [ "-O1" ] + common_optimize_on_cflags
   ldflags = common_optimize_on_ldflags
   visibility = [ ":default_optimization" ]
@@ -2192,7 +2163,8 @@
 #   configs += [ "//build/config/compiler:symbols" ]
 
 # Full symbols.
-config("symbols") {
+config("symbols") { }
+config("xsymbols") {
   if (is_win) {
     if (use_goma || is_clang) {
       # Note that with VC++ this requires is_win_fastlink, enforced elsewhere.
@@ -2290,7 +2262,8 @@
 # Minimal symbols.
 # This config guarantees to hold symbol for stack trace which are shown to user
 # when crash happens in unittests running on buildbot.
-config("minimal_symbols") {
+config("minimal_symbols") { }
+config("xminimal_symbols") {
   if (is_win) {
     # Linker symbols for backtraces only.
     cflags = []
@@ -2330,7 +2303,8 @@
 }
 
 # No symbols.
-config("no_symbols") {
+config("no_symbols") { }
+config("xno_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
     asmflags = cflags