Remove BuildInfo#isGreaterThanN()

The NMR1 SDK has been published upstream, so BuildInfo#isGreaterThanN is
no longer needed. This patch also removes reflection for
UserManager#isDemoUser() and ShortcutManager#reportShortcutUsed(),
and updates AndroidManifest.xml to remove the conditional include
of launchershortcut.xml and network_security_config.xml.

BUG=707302

Review-Url: https://codereview.chromium.org/2785373004
Cr-Original-Commit-Position: refs/heads/master@{#461787}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: df46c2242e4635dc77fce945bfc0ea0089efee31

android/lint/suppressions.xml

@@ -323,12 +323,6 @@ Still reading?
     <ignore regexp="chrome/android/java/res/drawable-hdpi/signin_promo_illustration.png"/>
     <ignore regexp="chrome/android/java/res/drawable-nodpi/missing.png"/>
     <ignore regexp="chrome/android/java/res/values-v17/styles.xml"/>
-    <!--
-        This file isn't used if the target SDK version is less than 24.
-        TODO(estevenson) remove this and the conditional inclusion in
-        AndroidManifest.xml after rolling to SDK 24.
-    -->
-    <ignore regexp="chrome/android/java/res/xml/network_security_config.xml"/>
     <ignore regexp="chromecast/browser/android/apk/res/values/strings.xml"/>
     <ignore regexp="chromecast/internal"/>
     <ignore regexp="clank"/>