Test to verify non-crash when there is an empty SVG path.

We already pass this test due to the way Blink manages path data
(directly using Skia's path).

R=pdr@chromium.org
BUG=254943

Review URL: https://chromiumcodereview.appspot.com/18181015

git-svn-id: svn://svn.chromium.org/blink/trunk@153290 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove unused "identifier" concept from WTFString

We don't use this bit anywhere. It was probably used to integrate with JSC.

R=eseidel
BUG=254708

Review URL: https://chromiumcodereview.appspot.com/18243004

git-svn-id: svn://svn.chromium.org/blink/trunk@153291 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove String's null termination machinery

We no longer use this machinery. We can remove it and free up a bit in
StringImpl.

R=eseidel
BUG=254708

Review URL: https://chromiumcodereview.appspot.com/18052030

git-svn-id: svn://svn.chromium.org/blink/trunk@153292 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Marked layout tests that will need to be rebaselined 
after https://codereview.chromium.org/17770004/ lands.

BUG=255667,233101

Review URL: https://chromiumcodereview.appspot.com/18227005

git-svn-id: svn://svn.chromium.org/blink/trunk@153293 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove AtomicStringImpl.

We believe it's a nop, and a confusing one at that.

BUG=250050

Review URL: https://chromiumcodereview.appspot.com/18228003

git-svn-id: svn://svn.chromium.org/blink/trunk@153294 bbb929c8-8fbe-4397-9dbb-9b2b20218538