Fixes for small width/height values in Android WebView quirks mode.

1) Classic WebView clamps up any viewport width values smaller
than 320 to the device size, and ignores the height values.  (This is a
generalization of the zero values quirk so I deleted that code.)

2) When changing the layout width due to wide viewport quirks, scaling
the height by the same amount could have strange results when the height
is specified.  Compute the height by aspect ratio instead.

NOTRY=true
BUG= internal b/11137060, b/11130064

Review URL: https://codereview.chromium.org/26299006

git-svn-id: svn://svn.chromium.org/blink/trunk@161384 bbb929c8-8fbe-4397-9dbb-9b2b20218538