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Added paragraph navigation and whole page caret browsing on Mac

A few text marker attributes are still missing from our Mac implementation.
This patch adds the missing attributes for paragraph and caret browsing.
This patch also declares any missing attributes for text markers in the form of constants,
instead of using text strings.
This is the full set of text marker attributes supported by Safari.
R=aleventhal@chromium.org
Bug: 990931

Change-Id: I9839f2f1f419c14b7730573ac1f7c1f3306f36c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1732692
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Auto-Submit: Nektarios Paisios <nektar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#684462}