Renamed "WebView" -> "WebViewImpl" in web_view.js and other files that import it

Imported from:
https://chromium.googlesource.com/chromium/src/+/a615ea0839c9276e80a7c0e66000dc7361ed68b6%5E%21/
Various webview cleanup

Imported from:
https://chromium.googlesource.com/chromium/src/+/848f1ed0482838d44ffd0bbbd3b8db0e5b6362c6%5E%21/
Moved parseSrcAttribute() into the SrcAttribute object as parse()

Imported from:
https://chromium.googlesource.com/chromium/src/+/3bc15760f9c7fb79cb3dd6064781c26ebbe1d5af%5E%21/