Fixes sessions restore crashes when the session is null (#1598)

Author: keianhzo

app/src/common/shared/org/mozilla/vrbrowser/VRBrowserActivity.java

@@ -929,7 +929,7 @@ private void handlePoorPerformance() {
             if (mPoorPerformanceWhiteList.contains(originalUrl)) {
                 return;
             }
-            window.getSessionStack().loadUri("about:blank");
+            window.getSessionStack().loadHomePage();
             final String[] buttons = {getString(R.string.ok_button), getString(R.string.performance_unblock_page)};
             window.showButtonPrompt(getString(R.string.performance_title), getString(R.string.performance_message), buttons, new ConfirmPromptWidget.ConfirmPromptDelegate() {
                 @Override

app/src/common/shared/org/mozilla/vrbrowser/browser/engine/SessionStack.java

@@ -58,7 +58,8 @@ public class SessionStack implements ContentBlocking.Delegate, GeckoSession.Navi
     private static final String LOGTAG = "VRB";
 
     // You can test a local file using: "resource://android/assets/webvr/index.html"
-    public static final String PRIVATE_BROWSING_URI = "about:privatebrowsing";
+    private static final String PRIVATE_BROWSING_URI = "about:privatebrowsing";
+    private static final String BLANK_BROWSING_URI = "about:blank";
     public static final int NO_SESSION = -1;
 
     private transient LinkedList<GeckoSession.NavigationDelegate> mNavigationListeners;
@@ -314,6 +315,10 @@ public void restore(SessionStack store, int currentSessionId) {
 
             if (mUsePrivateMode) {
                 loadPrivateBrowsingPage();
+
+            } else if(state.mSessionState == null || state.mUri.equals(BLANK_BROWSING_URI) ||
+                    (state.mSessionState != null && state.mSessionState.size() == 0)) {
+                loadHomePage();
             }
 
             dumpAllState(state.mSession);
@@ -641,6 +646,14 @@ public void loadUri(String aUri) {
         mCurrentSession.loadUri(aUri);
     }
 
+    public void loadHomePage() {
+        if (mCurrentSession == null) {
+            return;
+        }
+
+        mCurrentSession.loadUri(getHomeUri());
+    }
+
     public void loadPrivateBrowsingPage() {
         if (mCurrentSession == null) {
             return;

app/src/common/shared/org/mozilla/vrbrowser/browser/engine/SessionState.java

@@ -17,7 +17,7 @@
 import java.io.IOException;
 import java.util.ArrayList;
 
-@JsonAdapter(SessionState.SafeTypeAdapterFactory.class)
+@JsonAdapter(SessionState.SessionStateAdapterFactory.class)
 public class SessionState {
 
     public boolean mCanGoBack;
@@ -53,7 +53,7 @@ public GeckoSession.SessionState read(JsonReader in) {
         }
     }
 
-    public class SafeTypeAdapterFactory implements TypeAdapterFactory {
+    public class SessionStateAdapterFactory implements TypeAdapterFactory {
         public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
             final TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
             final TypeAdapter<GeckoSession.SessionState> gsDelegate = new GeckoSessionStateAdapter();
@@ -77,7 +77,12 @@ public void write(JsonWriter out, T value) throws IOException {
                                 out.name("mSessionState").jsonValue(null);
 
                             } else {
-                                out.name("mSessionState").jsonValue(gsDelegate.toJson(session.mSessionState));
+                                if (session.mSessionState != null) {
+                                    out.name("mSessionState").jsonValue(gsDelegate.toJson(session.mSessionState));
+
+                                } else {
+                                    out.name("mSessionState").jsonValue(null);
+                                }
                             }
                             out.endObject();