Merge "Revert "Clarify handling client certificates"" into mnc-dev

     * Notify the host application to handle a SSL client certificate

     * request. The host application is responsible for showing the UI

     * if desired and providing the keys. There are three ways to

     * respond: proceed(), cancel() or ignore(). Webview stores the response

     * in memory (for the life of the application) if proceed() or cancel() is

     * called and does not call onReceivedClientCertRequest() again for the

     * same host and port pair. Webview does not store the response if ignore()

     * is called.

     * respond: proceed(), cancel() or ignore(). Webview remembers the

     * response if proceed() or cancel() is called and does not

     * call onReceivedClientCertRequest() again for the same host and port

     * pair. Webview does not remember the response if ignore() is called.

     *

     * This method is called on the UI thread. During the callback, the

     * connection is suspended.

     *

     * For most use cases, the application program should implement the

     * {@link android.security.KeyChainAliasCallback} interface and pass it to

     * {@link android.security.KeyChain.choosePrivateKeyAlias} to start an

     * activity for the user to choose the proper alias. The keychain activity will

     * provide the alias through the callback method in the implemented interface. Next

     * the application should create an async task to call

     * {@link android.security.KeyChain.getPrivateKey} to receive the key.

     *

     * An example implementation of client certificates can be seen at

     * <A href="https://android.googlesource.com/platform/packages/apps/Browser/+/android-5.1.1_r1/src/com/android/browser/Tab.java">

     * AOSP Browser</a>

     *

     * The default behavior is to cancel, returning no client certificate.

     *

     * @param view The WebView that is initiating the callback