Make __DATE__ and __TIME__ to evaluate to an empty string.

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 60 matching lines @@
   # 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
 
   # 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
+
+  # Keep build metadata (__DATE__ and __TIME_) available.
+  # For the deterministic build, these parameters should be eliminated.
+  # See:  https://bugs.chromium.org/p/chromium/issues/detail?id=314403
+  enable_date_time_builtin_macro = false

[Dirk Pranke, 2016/08/22 17:31:45]

Does this even need to be easily toggleable? Why not just unconditionally set
the flags on line 217?

[M-A Ruel, 2016/08/22 19:16:53]

That's my opinion too, no need for a flag. Less flag is better.

[Yoshisato Yanagisawa, 2016/08/23 01:37:54]

I do not have strong opinions on whether to make it flags or not make it flags. 
Currently, __DATE__ seems only show up to flatc and I do not think it meaningful
to show actual date there.
Let me force the metadata eliminated.

 }
 
 if (is_clang && !is_nacl) {
   update_args = [ "--print-revision" ]
   if (llvm_force_head_revision) {
     update_args += [ "--llvm-force-head-revision" ]
   }
   clang_revision =
       exec_script("//tools/clang/scripts/update.py", update_args, "trim string")
 }
@@ skipping 109 matching lines @@
     }
 
     # Linker warnings.
     if (fatal_linker_warnings && !(is_chromeos && current_cpu == "arm") &&
         !(is_android && use_order_profiling) && !is_mac && !is_ios) {
       # TODO(jochen): Enable this on chromeos on arm. http://crbug.com/356580
       # TODO(lizeb,pasko): Fix link errors when linking with order_profiling=1
       # crbug.com/485542
       ldflags += [ "-Wl,--fatal-warnings" ]
     }
+
+    if (!enable_date_time_builtin_macro) {
+      cflags += [
+        "-Wno-builtin-macro-redefined",
+        "-D__DATE__=",
+        "-D__TIME__=",
+      ]
+    }
   }
 
   if (is_clang && is_debug) {
     # Allow comparing the address of references and 'this' against 0
     # in debug builds. Technically, these can never be null in
     # well-defined C/C++ and Clang can optimize such checks away in
     # release builds, but they may be used in asserts in debug builds.
     cflags_cc += [
       "-Wno-undefined-bool-conversion",
       "-Wno-tautological-undefined-compare",
@@ skipping 1348 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
   }
 }