Upstream constant related functions
* Moves some functions that deal TabState filenames to TabState
from TabPersistentStore downstream.
* Moves DOCUMENT_SCHEME from IntentHandler.java to UrlConstants.java
with similar schemes. Note that the DOCUMENT_SCHEME doesn't include
the "://" string like the other Java scheme constants; this is because
the Document classes use a real Uri parse to parse the scheme instead
of doing a plain old TextUtils.equals() comparison.
BUG=415747
Review URL: https://codereview.chromium.org/
796113003
Cr-Commit-Position: refs/heads/master@{#308011}