Update the user agent used in iOS 8.

BUG=391846
TEST=Go to whatsmyua.com on an iOS 8 device and verify that the
AppleWebKit and Safari versions in the user agent are the same in
MobileSafari and Chrome for iOS.

Review URL: https://codereview.chromium.org/558163003

Cr-Commit-Position: refs/heads/master@{#294168}

ios/web/public/user_agent.mm

@@ -33,6 +33,7 @@
   // Safari version can't be, so a lookup table is used instead (for both, since
   // the reported versions should stay in sync).
   static const OSVersionMap version_map[] = {
+    { 8, 0, { "600.1.4",   "600.1.4" } },
     { 7, 1, { "9537.53",   "537.51.2" } },
     { 7, 0, { "9537.53",   "537.51.1" } },
     // 6.1 has the same values as 6.0.