Switching iOS to use BoringSSL

This switches use_openssl on for iOS.

BUG=591545

Review URL: https://codereview.chromium.org/1872813002

Cr-Original-Commit-Position: refs/heads/master@{#387011}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 88283eca96ddc06440a778132f969a3e8360dbbf

common.gypi

@@ -265,11 +265,6 @@
             'enable_topchrome_md%': 1,
           }],
 
-          # On iOS, use NSS rather than OpenSSL. See http://crbug.com/338886.
-          ['OS=="ios"', {
-            'use_openssl%': 0,
-          }],
-
           # Enable App Launcher everywhere but mobile.
           ['OS!="ios" and OS!="android"', {
             'enable_app_list%': 1,

config/crypto.gni

@@ -12,9 +12,7 @@
 # to set up feature flags.
 
 declare_args() {
-  # Use OpenSSL instead of NSS. This is used for all platforms but iOS. (See
+  use_openssl = true
-  # http://crbug.com/338886).
-  use_openssl = !is_ios
 }
 
 # True when we're using OpenSSL for representing certificates. When targeting