Subpixel precision for clientWidth, offsetWidth, scrollTop et al

Change clientHeight, clientWidth, clientLeft, clientTop, scrollTop,
scrollLeft, scrollWidth, scrollHeight, offsetWidth, offsetHeight,
offsetTop, and offsetLeft to return precise floating point values
instead of rounded int values.

This matches the latest draft of the CSS OM Specification [1] and the
opt-in IE10 behavior [2].

Feature dashboard entry:
  http://www.chromestatus.com/features/5497402177880064

Intent to Implement & Ship:
  https://groups.google.com/a/chromium.org/d/msg/blink-dev/_Q7A4AQBFKY/S4ahQ5iE28QJ

R=ch.dumez@samsung.com, esprehn@chromium.org, leviw@chromium.org
BUG=360889
TEST=fast/sub-pixel/cssom-subpixel-precision.html,
     fast/sub-pixel/scroll-offset-precision.html

1: http://www.w3.org/TR/cssom-view/
2: http://blogs.msdn.com/b/ie/archive/2012/02/17/sub-pixel-rendering-and-the-css-object-model.aspx

Review URL: https://codereview.chromium.org/225263021

git-svn-id: svn://svn.chromium.org/blink/trunk@173053 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix regen of EventInterfaces.in by depending on list

Currently EventInterfaces.in isn't regenerated correctly if the *list*
of files changes -- it only rebuilds if one of the *files* is modified,
but not if a file is deleted, for instance.

This is fixed by explicitly depending on the list of files, which should
be done anyway (it's an argument to the command).

Documented at:
https://code.google.com/p/gyp/wiki/GypUserDocumentation

TBR=Nico
BUG=368875

Review URL: https://codereview.chromium.org/265803002

git-svn-id: svn://svn.chromium.org/blink/trunk@173054 bbb929c8-8fbe-4397-9dbb-9b2b20218538