Add FORCE_64BIT_ALIGN support to BUILD.gn

BUILD.gn

 # Copyright 2014 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.
 
 declare_args() {
   use_srtp_boringssl = true
 }
 
 config("libsrtp_config") {
   defines = [
@@ skipping 49 matching lines @@
 
   if (current_cpu == "arm" || current_cpu == "arm64" ||
       current_cpu == "mipsel" || current_cpu == "mips64el") {
     # TODO(leozwang): CPU_RISC doesn't work properly on android/arm and
     # mips platforms for unknown reasons, need to investigate the root
     # cause of it. CPU_RISC is used for optimization only, and CPU_CISC
     # should just work just fine, it has been tested on android/arm with
     # srtp test applications and libjingle.
     defines += [ "CPU_CISC" ]
   }
+  if (current_cpu == "mipsel" || current_cpu == "arm" || current_cpu == "x86") {
+    # Define FORCE_64BIT_ALIGN to avoid alignment-related-crashes like
+    # crbug/414919. Without this, aes_cbc_alloc will allocate an
+    # aes_cbc_ctx_t not 64-bit aligned and the v128_t members of
+    # aes_cbc_ctx_t will not be 64-bit aligned, which breaks the
+    # compiler optimizations that assume 64-bit alignment of v128_t.
+    defines += [ "FORCE_64BIT_ALIGN" ]
+  }
 }
 
 static_library("libsrtp") {
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   public_configs = [ ":libsrtp_config" ]
 
   sources = [
     # includes
     "srtp/include/ekt.h",
@@ skipping 289 matching lines @@
       ":srtp_test_stat_driver",
       ":srtp_test_sha1_driver",
       ":srtp_test_kernel_driver",
       ":srtp_test_aes_calc",
       ":srtp_test_rand_gen",
       ":srtp_test_rand_gen_soak",
       ":srtp_test_env",
     ]
   }
 }