Address the API review

Bug: 15432556

The api council asks to change the interface to an abstract class
and clarify the clearClientCertPreferences api. This change addresses
these.

Change-Id: I7979788c7c041bacbfef5ea4d94309f91279ef22

api/current.txt

@@ -34118,7 +34118,8 @@ package android.view.textservice {
 
 package android.webkit {
 
-  public abstract interface ClientCertRequest {
+  public abstract class ClientCertRequest {
+    ctor public ClientCertRequest();
     method public abstract void cancel();
     method public abstract java.lang.String getHost();
     method public abstract java.lang.String[] getKeyTypes();

core/java/android/webkit/ClientCertRequest.java

@@ -27,7 +27,7 @@ import java.security.cert.X509Certificate;
  * such as the host name and the port number requesting the cert, the acceptable
  * key types and the principals.
  *
- * The user should call one of the interface methods to indicate how to deal
+ * The user should call one of the class methods to indicate how to deal
  * with the client certificate request. All methods should be called on
  * UI thread.
  *
@@ -37,42 +37,45 @@ import java.security.cert.X509Certificate;
  * {@link WebView#clearClientCertPreferences}.
  *
  */
-public interface ClientCertRequest {
+public abstract class ClientCertRequest {
+
+    public ClientCertRequest() { }
+
     /**
      * Returns the acceptable types of asymmetric keys (can be null).
      */
-    public String[] getKeyTypes();
+    public abstract String[] getKeyTypes();
 
     /**
      * Returns the acceptable certificate issuers for the certificate
      *            matching the private key (can be null).
      */
-    public Principal[] getPrincipals();
+    public abstract Principal[] getPrincipals();
 
     /**
      * Returns the host name of the server requesting the certificate.
      */
-    public String getHost();
+    public abstract String getHost();
 
     /**
      * Returns the port number of the server requesting the certificate.
      */
-    public int getPort();
+    public abstract int getPort();
 
     /**
      * Proceed with the specified private key and client certificate chain.
      * Remember the user's positive choice and use it for future requests.
      */
-    public void proceed(PrivateKey privateKey, X509Certificate[] chain);
+    public abstract void proceed(PrivateKey privateKey, X509Certificate[] chain);
 
     /**
      * Ignore the request for now. Do not remember user's choice.
      */
-    public void ignore();
+    public abstract void ignore();
 
     /**
      * Cancel this request. Remember the user's choice and use it for
      * future requests.
      */
-    public void cancel();
+    public abstract void cancel();
 }

core/java/android/webkit/WebView.java

@@ -1486,11 +1486,11 @@ public class WebView extends AbsoluteLayout
     }
 
     /**
-     * Clears the client certificate preferences table stored in response
-     * to proceeding/cancelling client cert requests. Note that webview
+     * Clears the client certificate preferences stored in response
+     * to proceeding/cancelling client cert requests. Note that Webview
      * automatically clears these preferences when it receives a
-     * {@link KeyChain#ACTION_STORAGE_CHANGED} intent. The client certificate
-     * preferences are global for all Webviews.
+     * {@link KeyChain#ACTION_STORAGE_CHANGED} intent. The preferences are
+     * shared by all the webviews that are created by the embedder application.
      *
      * @param onCleared  A runnable to be invoked when client certs are cleared.
      *                   The embedder can pass null if not interested in the