Avoid to use abbreviated names in {first,last}EditableVisiblePosition{After,Before}PositionInRoot

This patch renames abbreviated name "p" to "editablePosition" in {first,last}EditableVisiblePosition{After,Before}PositionInRoot for improving readability and ease of maintenance.

This patch is a preparation of introducing |lastEditablePositionBeforePositionInRoot.

BUG=n/a
TEST=n/a; no behavior changes

Review URL: https://codereview.chromium.org/342553008

git-svn-id: svn://svn.chromium.org/blink/trunk@176491 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Check before setting initial border image styles

Border-image and its friend mask-box-image are shorthands that
expand out into 4 css properties[1]. When setting the initial values
for these we would blindly create a new NinePieceBorderImage which
is large and contains non-trivial destructors. This patch first
checks whether the current value is already equal to the initial value
before setting.

[1] https://developer.mozilla.org/en-US/docs/Web/CSS/border-image

Review URL: https://codereview.chromium.org/340703004

git-svn-id: svn://svn.chromium.org/blink/trunk@176492 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move divider detection and creation onto TimelineUIUtils instance

BUG=361045
R=loislo@chromium.org

Review URL: https://codereview.chromium.org/339493006

git-svn-id: svn://svn.chromium.org/blink/trunk@176493 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Extend WebFallbackFont by fciId

Required for instantiating the fallback fonts from the sandbox since
this instantiation is not allowed by filename, but only through
Skia's SkFontConfigInterface, where paths are previously kept track
of in the Linux sandbox support process.
Preparation for a Chromium side change which fills fciId.

BUG=285303
R=abarth,eae

Review URL: https://codereview.chromium.org/340073002

git-svn-id: svn://svn.chromium.org/blink/trunk@176494 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move needsPreviewElement to TimelineUIUtilsImple and make it private

Drive-by: removed formatter for counters field which is not in the protocol anymore.

BUG=361045
R=loislo@chromium.org

Review URL: https://codereview.chromium.org/343613004

git-svn-id: svn://svn.chromium.org/blink/trunk@176495 bbb929c8-8fbe-4397-9dbb-9b2b20218538