Back button for share activity.

src/org/thoughtcrime/securesms/ShareActivity.java

@@ -32,6 +32,7 @@ import android.widget.ImageView;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.appcompat.app.ActionBar;
 import androidx.appcompat.widget.Toolbar;
 
 import org.thoughtcrime.securesms.components.SearchToolbar;
@@ -151,6 +152,9 @@ public class ShareActivity extends PassphraseRequiredActionBarActivity
   private void initializeToolbar() {
     Toolbar toolbar = findViewById(R.id.toolbar);
     setSupportActionBar(toolbar);
+    ActionBar actionBar = getSupportActionBar();
+    actionBar.setDisplayHomeAsUpEnabled(true);
+    actionBar.setHomeButtonEnabled(true);
   }
 
   private void initializeResources() {