Annotate Notification.Action.Builder building methods with @NonNull.

Annotate all Builder methods returning the Build objects as @NonNull,
this is to support Kotlin developers.

Bug: 126698549
Test: N/A
Change-Id: I147a61d73f7d819571dfe97f1b55d4c79cffbf52
diff --git a/core/java/android/app/Notification.java b/core/java/android/app/Notification.java
index 2e7093d..639416a 100644
--- a/core/java/android/app/Notification.java
+++ b/core/java/android/app/Notification.java
@@ -1629,6 +1629,7 @@
              *
              * @see Notification.Action#extras
              */
+            @NonNull
             public Builder addExtras(Bundle extras) {
                 if (extras != null) {
                     mExtras.putAll(extras);
@@ -1652,6 +1653,7 @@
              * @param remoteInput a {@link RemoteInput} to add to the action
              * @return this object for method chaining
              */
+            @NonNull
             public Builder addRemoteInput(RemoteInput remoteInput) {
                 if (mRemoteInputs == null) {
                     mRemoteInputs = new ArrayList<RemoteInput>();
@@ -1669,6 +1671,7 @@
              * @return this object for method chaining
              * The default value is {@code true}
              */
+            @NonNull
             public Builder setAllowGeneratedReplies(boolean allowGeneratedReplies) {
                 mAllowGeneratedReplies = allowGeneratedReplies;
                 return this;
@@ -1682,6 +1685,7 @@
              * {@code SEMANTIC_ACTION_} prefixes
              * @return this object for method chaining
              */
+            @NonNull
             public Builder setSemanticAction(@SemanticAction int semanticAction) {
                 mSemanticAction = semanticAction;
                 return this;
@@ -1692,6 +1696,7 @@
              * dependent on the notification message body. An example of a contextual action could
              * be an action opening a map application with an address shown in the notification.
              */
+            @NonNull
             public Builder setContextual(boolean isContextual) {
                 mIsContextual = isContextual;
                 return this;
@@ -1701,6 +1706,7 @@
              * Apply an extender to this action builder. Extenders may be used to add
              * metadata or change options on this builder.
              */
+            @NonNull
             public Builder extend(Extender extender) {
                 extender.extend(this);
                 return this;
@@ -1728,6 +1734,7 @@
              * object.
              * @return the built action
              */
+            @NonNull
             public Action build() {
                 checkContextualActionNullFields();