Add Keep-Alive to HttpHeaders.

RELNOTES=`net`: Added `HttpHeaders` constant for Keep-Alive.
PiperOrigin-RevId: 378743056

Author: java-team-github-bot

android/guava/src/com/google/common/net/HttpHeaders.java

@@ -304,6 +304,12 @@ private ReferrerPolicyValues() {}
   public static final String LINK = "Link";
   /** The HTTP {@code Location} header field name. */
   public static final String LOCATION = "Location";
+  /**
+   * The HTTP {@code Keep-Alive} header field name.
+   *
+   * @since NEXT
+   */
+  public static final String KEEP_ALIVE = "Keep-Alive";
   /**
    * The HTTP <a href="https://googlechrome.github.io/OriginTrials/#header">{@code Origin-Trial}</a>
    * header field name.

guava/src/com/google/common/net/HttpHeaders.java

@@ -304,6 +304,12 @@ private ReferrerPolicyValues() {}
   public static final String LINK = "Link";
   /** The HTTP {@code Location} header field name. */
   public static final String LOCATION = "Location";
+  /**
+   * The HTTP {@code Keep-Alive} header field name.
+   *
+   * @since NEXT
+   */
+  public static final String KEEP_ALIVE = "Keep-Alive";
   /**
    * The HTTP <a href="https://googlechrome.github.io/OriginTrials/#header">{@code Origin-Trial}</a>
    * header field name.