Revert of Change //build/config/compiler:optimize_max to use -O3.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 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/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/toolchain.gni")
@@ skipping 1355 matching lines @@
           "/GL",  # Whole program optimization.
 
           # Disable Warning 4702 ("Unreachable code") for the WPO/PGO builds.
           # Probably anything that this would catch that wouldn't be caught in a
           # normal build isn't going to actually be a bug, so the incremental
           # value of C4702 for PGO builds is likely very small.
           "/wd4702",
         ]
       }
     } else {
-      cflags = [ "-O3" ] + common_optimize_on_cflags
+      cflags = [ "-O2" ] + common_optimize_on_cflags
     }
   }
 }
 
 # The default optimization applied to all targets. This will be equivalent to
 # either "optimize" or "no_optimize", depending on the build flags.
 config("default_optimization") {
   if (is_nacl_irt) {
     # The NaCl IRT is a special case and always wants its own config.
     # It gets optimized the same way regardless of the type of build.
@@ skipping 93 matching lines @@
 
 if (is_ios || is_mac) {
   # On Mac and iOS, this enables support for ARC (automatic ref-counting).
   # See http://clang.llvm.org/docs/AutomaticReferenceCounting.html.
   config("enable_arc") {
     common_flags = [ "-fobjc-arc" ]
     cflags_objc = common_flags
     cflags_objcc = common_flags
   }
 }