Bug 1517846 - Add missing docs for GeckoView.releaseSession() r=geckoview-reviewers,esawin#geckoview-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D15753

--HG--
extra : moz-landing-system : lando

mobile/android/geckoview/api.txt

@@ -705,9 +705,9 @@ package org.mozilla.geckoview {
     method @android.support.annotation.AnyThread @android.support.annotation.NonNull public org.mozilla.gecko.EventDispatcher getEventDispatcher();
     method @android.support.annotation.NonNull public org.mozilla.geckoview.PanZoomController getPanZoomController();
     method @android.support.annotation.AnyThread @android.support.annotation.Nullable public org.mozilla.geckoview.GeckoSession getSession();
-    method @android.support.annotation.Nullable public org.mozilla.geckoview.GeckoSession releaseSession();
-    method public void setSession(@android.support.annotation.NonNull org.mozilla.geckoview.GeckoSession);
-    method public void setSession(@android.support.annotation.NonNull org.mozilla.geckoview.GeckoSession, @android.support.annotation.Nullable org.mozilla.geckoview.GeckoRuntime);
+    method @android.support.annotation.UiThread @android.support.annotation.Nullable public org.mozilla.geckoview.GeckoSession releaseSession();
+    method @android.support.annotation.UiThread public void setSession(@android.support.annotation.NonNull org.mozilla.geckoview.GeckoSession);
+    method @android.support.annotation.UiThread public void setSession(@android.support.annotation.NonNull org.mozilla.geckoview.GeckoSession, @android.support.annotation.Nullable org.mozilla.geckoview.GeckoRuntime);
     method public boolean shouldPinOnScreen();
     field protected final org.mozilla.geckoview.GeckoView.Display mDisplay;
     field protected org.mozilla.geckoview.GeckoRuntime mRuntime;

mobile/android/geckoview/src/main/java/org/mozilla/geckoview/GeckoView.java

@@ -242,6 +242,14 @@ public class GeckoView extends FrameLayout {
         }
     }
 
+    /**
+     * Unsets the current session from this instance and returns it, if any. You must call
+     * this before {@link #setSession(GeckoSession)} if there is already an open session
+     * set for this instance.
+     *
+     * @return The {@link GeckoSession} that was set for this instance. May be null.
+     */
+    @UiThread
     public @Nullable GeckoSession releaseSession() {
         ThreadUtils.assertOnUiThread();
 
@@ -279,10 +287,14 @@ public class GeckoView extends FrameLayout {
 
     /**
      * Attach a session to this view. The session should be opened before
-     * attaching.
+     * attaching. If this instance already has an open session, you must use
+     * {@link #releaseSession()} first, otherwise {@link IllegalStateException}
+     * will be thrown. This is to avoid potentially leaking the currently opened session.
      *
      * @param session The session to be attached.
+     * @throws IllegalArgumentException if an existing open session is already set.
      */
+    @UiThread
     public void setSession(@NonNull final GeckoSession session) {
         ThreadUtils.assertOnUiThread();
 
@@ -296,10 +308,15 @@ public class GeckoView extends FrameLayout {
     /**
      * Attach a session to this view. The session should be opened before
      * attaching or a runtime needs to be provided for automatic opening.
+     * If this instance already has an open session, you must use
+     * {@link #releaseSession()} first, otherwise {@link IllegalStateException}
+     * will be thrown. This is to avoid potentially leaking the currently opened session.
      *
      * @param session The session to be attached.
      * @param runtime The runtime to be used for opening the session.
+     * @throws IllegalArgumentException if an existing open session is already set.
      */
+    @UiThread
     public void setSession(@NonNull final GeckoSession session,
                            @Nullable final GeckoRuntime runtime) {
         ThreadUtils.assertOnUiThread();

mobile/android/geckoview/src/main/java/org/mozilla/geckoview/doc-files/CHANGELOG.md

@@ -21,6 +21,8 @@ layout: geckoview
 - Added GeckoRuntimeSetting for enabling desktop viewport. Desktop viewport is
   no longer set by `USER_AGENT_MODE_DESKTOP` and must be set separately.
 
+- Added `@UiThread` to `GeckoSession.releaseSession` and `GeckoSession.setSession`
+
 ## v65
 - Moved [`CompositorController`][65.1], [`DynamicToolbarAnimator`][65.2],
   [`OverscrollEdgeEffect`][65.3], [`PanZoomController`][65.4] from