Reduce TextIterator dependency from accessibility module

This patch reduces TextIterator dependency from accessibility module. The usage of TextIterator is only in AXRenderObject.

BUG=n/a
TEST=n/a; no behavior changes
R=tkent@chromium.org

Review URL: https://codereview.chromium.org/35773003

git-svn-id: svn://svn.chromium.org/blink/trunk@160305 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Web Animations CSS: Implement TransitionTimeline

This patch adds a separate timeline for CSS transitions. This fixes a
couple of problems of using the same timeline -- we can now correctly
apply transitions at the last step of the cascade, and we can also run
transitions before the document has been loaded.

This requires several changes to support it. We add a 'priority'
field to Animation to determine whether we are a CSS Transition or
other Animation (the Animations go to the same AnimationStack).
The logic for getting the compositable values to apply is moved to
the AnimationStack, and CSSAnimations determines the new/cancelled
animations. We also no longer recompute the compositable values in
each applyAnimatedProperties pass, instead doing this once for each
of transitions and animations beforehand.

BUG=303430

Review URL: https://codereview.chromium.org/27372007

git-svn-id: svn://svn.chromium.org/blink/trunk@160306 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move SecurityContext to Document and WorkerGlobalScope superclass.

This change moves SecurityContext from superclass of ExecutionContext
to one of Document and WorkerGlobalScope. Now security origin
and CSP is provided to ExecutionContext from its clients.

In coming change, ExecutionContext will move to DOMWindow superclass
from Document superclass so that DOMWindow and scripting state
is shared between imported documents.

BUG=305497
R=abarth, dglazkov

Review URL: https://codereview.chromium.org/34793002

git-svn-id: svn://svn.chromium.org/blink/trunk@160307 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Change namespace of WebCore::PlainTextRange to WebCore::AXObject::PlainTextRange

This patch changes namespace of Change namespace of WebCore::PlainTextRange to WebCore::AXObject::PlainTextRange for using WebCore::PlainTextRange in editing module, e.g. TextIterator, InputMethodController and WebViewImpl. We don't want to use editing/PlainTextRange in accessibility, because it will have more functions for editing, e.g. PlainTextRange::fromRange(),  PlainTextRange::fromRange(), and so on.

This patch also removes unused member functions, AXObject::selectionStart() and AXObject::selectionEnd().

BUG=n/a
TEST=n/a; no behavior changes
R=dmazzoni@chromium.org, tkent@chromium.org

Review URL: https://codereview.chromium.org/35743007

git-svn-id: svn://svn.chromium.org/blink/trunk@160308 bbb929c8-8fbe-4397-9dbb-9b2b20218538