BrowserSettings: update desktop UA string to match Chrome 30

Now that we're using a Chromium-based WebView which closely matches
Chrome 30, we should report as a newer Chrome version when masquerading
as a desktop browser.

Change-Id: I301a8cfac9a83e66a6749872943e80ff5c4740a1
Merge "BrowserSettings: update desktop UA string to match Chrome 30" into du44