Move mutation event histogramming over to UseCounter.

This gets rid of the one-off code and also changes it so we count
once per Page instead of once per Document.

Review URL: https://chromiumcodereview.appspot.com/24135002

git-svn-id: svn://svn.chromium.org/blink/trunk@157738 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[SVG] Interval should not be created if a value in begin-value-list doesn't have a matching value in end-value-list

In the pseudo code in http://www.w3.org/TR/SMIL3/smil-timing.html#q90 ,
it says that if all ends are before the current begin, then it is a bad interval and current begin will be discarded.
Existing code is treating it as a vaild interval with end as indefinite.
Modified the logic to be in line with the pseudo code.

R=pdr@chromium.org, schenney@chromium.org, dschulze@chromium.org, fmalita@chromium.org
BUG=269059

Review URL: https://chromiumcodereview.appspot.com/22604002

git-svn-id: svn://svn.chromium.org/blink/trunk@157739 bbb929c8-8fbe-4397-9dbb-9b2b20218538