docs: Changing "http" to "https" in Javadoc examples

Several of the Javadoc comments had code snippets that used "http"
web addresses (e.g. "http://example.com"). Our style heavily
recommends using https whenever possible; in addition, this caused
the generated Javadoc files to fail presubmit checks when we try
to migrate them to Piper (see, e.g., http://cl/155212684)

In addition, one code snipped used (as an example) a link to
http://slashdot.org/ ; we really shouldn't be using links to real
websited (that we don't control) unless we absolutely have to.

I changed all the examples to "https://example.com/" ; I've verified
that that's a valid URL (they've got a good certificate).

Generated the doc and staged it to:
go/dac-stage/reference/android/webkit/WebView.html

Test: make ds-docs
Bug: 37996959
Change-Id: Id8e44930b107b94022376a260892ed867ba281fc