[Android] Fixed error that file not found in CrosswalkSample

The url of initial page in sample of onCreateWindowRequested is the
old one which already not present in the assets folder.

This error is caused by the following commit:
5edf99d333377ae6866860f36348d891652cf8ce
[Android] Add sample and test cases for Embedding API
Merge pull request #2603 from lincsoon/TestEmbeddingAPI

[Android] Fixed error that file not found in CrosswalkSample