Make ~WebContentSettingsClient public and virtual
Make ~WebContentSettingsClient public and virtual

Currently, the destructor of WebContentSettingsClient is non-virtual and protected. The interface itself has a number of virtual methods.

In https://codereview.chromium.org/1078263003, I would like to create scoped_ptr to implementations of WebContentSettingsClient, without specifying concrete implementations. I would like to be able to create a scoped_ptr<WebContentSettingsClient>.

To make such a thing compile, I need ~WebContentSettingsClient to be public.
To make such a thing correct, I need ~WebContentSettingsClient to be virtual.

Is this in line with blink's style?

R=mkwst@chromium.org
BUG=384874

Review URL: https://codereview.chromium.org/1076293003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@193596 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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