[DO NOT MERGE] Uses javascript to assert the autofilled values on WebView tests.

We were overriding autofill() on such assertions, which only asserts that
the framework is calling webview's autofill(), but not the effective WebView
implementation per se.

Test: WebViewActivityTest
Bug: 110277265
Bug: 184006394
Merged-In: I1466721bd6dc4e526c56d74d51399a6d83771898
(cherry picked from commit 5741d196d051b3b27e227bf568a7ef48b926af93)

Change-Id: I07d3804cab50ad4d7796f7f9cc23487f90fcd759
3 files changed