build: Enable optimize_for_size unconditionally.

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/chromecast_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/toolchain.gni")
@@ skipping 56 matching lines @@
     # The patch is preapplied to the internal toolchain and hence all bots.
     msvs_xtree_patched = false
   }
 
   # Omit unwind support in official builds to save space.
   # We can use breakpad for these builds.
   exclude_unwind_tables = (is_chrome_branded && is_official_build) ||
                           (is_chromecast && !is_cast_desktop_build && !is_debug)
 
   # If true, optimize for size. Does not affect windows builds.
-  # Linux & Mac favor speed over size.
-  # TODO(brettw) it's weird that Mac and desktop Linux are different. We should
-  # explore favoring size over speed in this case as well.
-  optimize_for_size = is_android || is_ios
+  optimize_for_size = true
 
   # Enable fatal linker warnings. Building Chromium with certain versions
   # of binutils can cause linker warning.
   # See: https://bugs.chromium.org/p/chromium/issues/detail?id=457359
   fatal_linker_warnings = true
 
   # Build with C++ RTTI enabled. Chromium builds without RTTI by default,
   # but some sanitizers are known to require it, like CFI diagnostics
   # and UBsan variants.
   use_rtti = use_cfi_diag || is_ubsan_vptr || is_ubsan_security
@@ skipping 1662 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
   }
 }