CSS Animations: Add a helper script for building interpolation tests

The current animation-test-helper is prone to flakiness and impossible
to use across browsers. This change adds a new helper which make it
possible to write fast, non-flaky, cross-browser tests which exercise
interpolation logic.

Review URL: https://chromiumcodereview.appspot.com/23412003

git-svn-id: svn://svn.chromium.org/blink/trunk@156755 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Merge HTMLBodyElement::didNotifySubtreeInsertions into HTMLBodyElement::insertedInto

The logic in didNotifySubtreeInsertions to set the marginwidth and marginheight attributes
on the <body> of elements inside <iframe> and <frame> doesn't need to run after inserting
all the children of the frame. In fact this means that when you have those attributes
and then the script in the iframe touches offsetLeft or any layout dependent property
we'll layout with the wrong values and then have to do another layout after these margin
attributes are set.

I also remove the scheduleRelayout() call that was inside didNotifySubtreeInsertions. This
call doesn't make any sense, inserting a <body> will always trigger a style recalc and
a subsequent layout. The code is 9 years old: https://trac.webkit.org/changeset/8122
and all tests run fine without it.

Review URL: https://chromiumcodereview.appspot.com/23500002

git-svn-id: svn://svn.chromium.org/blink/trunk@156756 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move fast/check-layout-error-no-attributes to fast/harness

And also fix the test so that we're not printing "FAIL:" when the
test is actually passing.

R=ojan@chromium.org
BUG=233956

Review URL: https://chromiumcodereview.appspot.com/23476004

git-svn-id: svn://svn.chromium.org/blink/trunk@156757 bbb929c8-8fbe-4397-9dbb-9b2b20218538
FrameLoaderClientImpl::createFrame does not need marginWidth, marginHeight or allowsScrolling arguments

createFrame ignores all these arguments so we can remove them which means we can
remove HTMLFrameOwnerElement::marginWidth(), marginHeight() and allowScrollingInContentFrame()
in addition to making HTMLFrameElementBase::marginHeight() and marginWidth() non-virtual.

Review URL: https://chromiumcodereview.appspot.com/23498003

git-svn-id: svn://svn.chromium.org/blink/trunk@156758 bbb929c8-8fbe-4397-9dbb-9b2b20218538
XMLErrors::insertErrorMessageBlock does not need to call detach

parserRemoveChild already does a detach(), there's no reason for
insertErrorMessageBlock to do it.

Review URL: https://chromiumcodereview.appspot.com/23493004

git-svn-id: svn://svn.chromium.org/blink/trunk@156759 bbb929c8-8fbe-4397-9dbb-9b2b20218538