Revert of Handle Java assert using a customized function in base

chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/HostBrowserClassLoader.java

Index: chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/HostBrowserClassLoader.java
diff --git a/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/HostBrowserClassLoader.java b/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/HostBrowserClassLoader.java
index 84ddce5938629cc5ff17c2c83c0584fcfd0f9a8e..f358e6211dc2948ffeb5d8094babc386c6de68e6 100644
--- a/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/HostBrowserClassLoader.java
+++ b/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/HostBrowserClassLoader.java
@@ -7,6 +7,7 @@
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.content.pm.PackageManager;
+import android.os.Looper;
 import android.util.Log;
 
 import org.chromium.webapk.lib.common.WebApkConstants;
@@ -50,6 +51,7 @@
      * @return The ClassLoader.
      */
     public static ClassLoader getClassLoaderInstance(Context context, String canaryClassName) {
+        assertRunningOnUiThread();
         Context remoteContext = WebApkUtils.getHostBrowserContext(context);
         if (remoteContext == null) {
             Log.w(TAG, "Failed to get remote context.");
@@ -171,4 +173,11 @@
         }
         return value;
     }
+
+    /**
+     * Asserts that current thread is the UI thread.
+     */
+    private static void assertRunningOnUiThread() {
+        assert Looper.getMainLooper().equals(Looper.myLooper());
+    }
 }