Update net/third_party/nss to NSS_3_15_5_BETA2.

net/third_party/nss/README.chromium

 Name: Network Security Services (NSS)
 URL: http://www.mozilla.org/projects/security/pki/nss/
-Version: 3.15.4
+Version: 3.15.5 Beta 2
 Security Critical: Yes
 License: MPL 2
 License File: NOT_SHIPPED
 
 This directory includes a copy of NSS's libssl from the hg repo at:
   https://hg.mozilla.org/projects/nss
 
 The same module appears in crypto/third_party/nss (and third_party/nss on some
 platforms), so we don't repeat the license file here.
 
-The snapshot was updated to the hg tag: NSS_3_15_4_RTM
+The snapshot was updated to the hg tag: NSS_3_15_5_BETA2
 
 Patches:
 
   * Cache the peer's intermediate CA certificates in session ID, so that
     they're available when we resume a session.
     patches/cachecerts.patch
     https://bugzilla.mozilla.org/show_bug.cgi?id=731478
 
   * Add support for client auth with native crypto APIs on Mac and Windows.
     patches/clientauth.patch
@@ skipping 30 matching lines @@
     patches/suitebonly.patch
 
   * Define the SECItemArray type and declare the SECItemArray handling
     functions, which were added in NSS 3.15. Remove this patch when all system
     NSS packages are NSS 3.15 or later.
     patches/secitemarray.patch
 
   * Update Chromium-specific code for TLS 1.2.
     patches/tls12chromium.patch
 
-  * Add the Application Layer Protocol Negotiation extension.
-    patches/alpn.patch
-
   * Add Chromium-specific code to detect AES GCM support in the system NSS
     libraries at run time. Remove this patch when all system NSS packages are
     NSS 3.15 or later.
     patches/aesgcmchromium.patch
 
   * Support ChaCha20+Poly1305 ciphersuites
     http://tools.ietf.org/html/draft-agl-tls-chacha20poly1305-01
     patches/chacha20poly1305.patch
 
   * Fix session cache lock creation race.
     patches/cachelocks.patch
     https://bugzilla.mozilla.org/show_bug.cgi?id=764646
 
-  * In the case that a ClientHello record is between 256 and 511 bytes long,
-    add an extension to make it 512 bytes. This works around a bug in F5
-    terminators.
-    patches/paddingextension.patch
+  * Always add an extension to a ClientHello to make it 512 bytes.
     patches/paddingextensionall.patch
-    https://bugzilla.mozilla.org/show_bug.cgi?id=944157
 
   * Support the Certificate Transparency (RFC 6962) TLS extension
     signed_certificate_timestamp (client only).
     patches/signedcertificatetimestamps.patch
     https://bugzilla.mozilla.org/show_bug.cgi?id=944175
 
   * Add a function to allow the cipher suites preference order to be set.
     patches/cipherorder.patch
 
   * Add TLS_FALLBACK_SCSV cipher suite to version fallback connections.
@@ skipping 12 matching lines @@
   * Use NSSRWLock instead of PRRWLock in sslSessionID. This avoids the bugs
     in the lock rank checking code in PRRWLock.
     patches/nssrwlock.patch
     https://bugzilla.mozilla.org/show_bug.cgi?id=957812
 
 Apply the patches to NSS by running the patches/applypatches.sh script.  Read
 the comments at the top of patches/applypatches.sh for instructions.
 
 The ssl/bodge directory contains files taken from the NSS repo that we required
 for building libssl outside of its usual build environment.