WebView: refactor testGetOriginalUrl

This splits up a large code block inside onMainThreadSync(). This adds
necessary methods to WebViewOnUiThread.

Bug: 440431456
Test: atest CtsWebkitTestCases:WebViewTest#testGetOriginalUrl
Test: atest CtsWebkitTestCases:WebViewTest#testLoadUrl
Flag: TEST_ONLY
Change-Id: Ie8a0334b54ccbc1519c3838d118259d40cf7d586
2 files changed