Revert 169211 "Compute the keyTimes index correctly for discrete..."

The following tests crash on debug bots:
svg/W3C-SVG-1.1/animate-elem-11-t.svg,svg/W3C-SVG-1.1/animate-elem-15-t.svg,svg/W3C-SVG-1.1/animate-elem-82-t.svg,svg/animations/animate-elem-11-t-drt.html,svg/animations/animate-elem-15-t-drt.html,svg/animations/animate-keytimes-crash.html,svg/animations/animateMotion-multiple.html,svg/animations/mozilla/animateMotion-to-overridden-1.svg

One example: http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Mac10.6%20%28dbg%29/builds/13222/steps/webkit_tests/logs/stdio

> Compute the keyTimes index correctly for discrete (values) animations
> 
> The last value is allowed to be non-one for discrete mode animations (but
> not for linear and spline mode animations).
> 
> TEST=svg/animations/animate-elem-{14,18}-t-drt.html
> BUG=350318
> 
> Review URL: https://codereview.chromium.org/197283002

TBR=fs@opera.com

Review URL: https://codereview.chromium.org/196653016

git-svn-id: svn://svn.chromium.org/blink/trunk@169261 bbb929c8-8fbe-4397-9dbb-9b2b20218538