[Paint Preview] Fix failed assertion in PseudoTab

This assertion can fail because this path is now also accessible if
PAINT_PREVIEW_SHOW_ON_STARTUP flag is enabled.
It was added here: crrev.com/c/2472432

Bug: 1134752
Change-Id: I20d8937b24de77c366a8bf552a68ff787d488959
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2485395
Commit-Queue: Mehran Mahmoudi <mahmoudi@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818561}

chrome/android/features/tab_ui/java/src/org/chromium/chrome/browser/tasks/pseudotab/PseudoTab.java

@@ -314,7 +314,8 @@ public class PseudoTab {
     }
 
     private static void readAllPseudoTabsFromStateFile() {
-        assert CachedFeatureFlags.isEnabled(ChromeFeatureList.INSTANT_START);
+        assert CachedFeatureFlags.isEnabled(ChromeFeatureList.INSTANT_START)
+                || CachedFeatureFlags.isEnabled(ChromeFeatureList.PAINT_PREVIEW_SHOW_ON_STARTUP);
         if (sReadStateFile) return;
         sReadStateFile = true;