Bug 1434126 - Call GeckoSession.closeWindow() from onDestroy() in CustomTabsActivity and WebAppActivity. r=snorp

mobile/android/base/java/org/mozilla/gecko/customtabs/CustomTabsActivity.java

@@ -179,6 +179,7 @@ public class CustomTabsActivity extends AppCompatActivity
 
     @Override
     public void onDestroy() {
+        mGeckoSession.closeWindow();
         mTextSelection.destroy();
         mFormAssistPopup.destroy();
         mDoorHangerPopup.destroy();

mobile/android/base/java/org/mozilla/gecko/webapps/WebAppActivity.java

@@ -217,6 +217,7 @@ public class WebAppActivity extends AppCompatActivity
 
     @Override
     public void onDestroy() {
+        mGeckoSession.closeWindow();
         mTextSelection.destroy();
         mDoorHangerPopup.destroy();
         mPromptService.destroy();

mobile/android/geckoview/src/main/java/org/mozilla/gecko/GeckoSession.java

@@ -565,7 +565,8 @@ public class GeckoSession extends LayerSession
         ThreadUtils.assertOnUiThread();
 
         if (!isOpen()) {
-            throw new IllegalStateException("Session is not open");
+            Log.w(LOGTAG, "Attempted to close a GeckoSession that was already closed.");
+            return;
         }
 
         if (GeckoThread.isStateAtLeast(GeckoThread.State.PROFILE_READY)) {