Introduce USE_OPENSSL_CERTS for certificate handling.

crypto/crypto.gyp

Index: crypto/crypto.gyp
diff --git a/crypto/crypto.gyp b/crypto/crypto.gyp
index 3a493fbe4b58a27938607ed7484dc708a2122a22..aa9a1fba00f8a013353cb1bcbe14902fe333ad9b 100644
--- a/crypto/crypto.gyp
+++ b/crypto/crypto.gyp
@@ -80,7 +80,7 @@
             'mac_security_services_lock.h',
           ],
         }],
-        [ 'OS == "mac" or OS == "ios" or OS == "win"', {
+        [ 'use_openssl == 0 and (OS == "mac" or OS == "ios" or OS == "win")', {
           'dependencies': [
             '../third_party/nss/nss.gyp:nspr',
             '../third_party/nss/nss.gyp:nss',
@@ -200,16 +200,6 @@
             'openpgp_symmetric_encryption_unittest.cc',
           ]
         }],
-        [ 'OS == "mac" or OS == "ios" or OS == "win"', {
-          'dependencies': [
-            '../third_party/nss/nss.gyp:nss',
-          ],
-        }],
-        [ 'OS == "mac"', {
-          'dependencies': [
-            '../third_party/nss/nss.gyp:nspr',
-          ],
-        }],
         [ 'OS == "win"', {
           # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
           'msvs_disabled_warnings': [4267, ],