Add NET_EXPORT for CreateX509CertificateFromBuffers so that component build works

Bug: None
Test: Build no longer fails with linker errors for this function.
Change-Id: I0b126ae80f01b659dbc679f34f465322eecb7282
Reviewed-on: https://chromium-review.googlesource.com/c/1258210Reviewed-by: Matt Mueller <mattm@chromium.org>
Commit-Queue: Matt Swartwout <mwswartwout@google.com>
Cr-Commit-Position: refs/heads/master@{#596044}

net/cert/x509_util.h

@@ -34,9 +34,7 @@ class X509Certificate;
 namespace x509_util {
 
 // Supported digest algorithms for signing certificates.
-enum DigestAlgorithm {
-  DIGEST_SHA256
-};
+enum DigestAlgorithm { DIGEST_SHA256 };
 
 // Generate a 'tls-server-end-point' channel binding based on the specified
 // certificate. Channel bindings are based on RFC 5929.
@@ -120,7 +118,7 @@ NET_EXPORT base::StringPiece CryptoBufferAsStringPiece(
 
 // Creates a new X509Certificate from the chain in |buffers|, which must have at
 // least one element.
-scoped_refptr<X509Certificate> CreateX509CertificateFromBuffers(
+NET_EXPORT scoped_refptr<X509Certificate> CreateX509CertificateFromBuffers(
     const STACK_OF(CRYPTO_BUFFER) * buffers);
 
 // Returns the default ParseCertificateOptions for the net stack.