Revert of [Android Refactor] Merge WebappDataStorage#LAST_USED_UNSET and LAST_USED_INVALID

Revert of [Android Refactor] Merge WebappDataStorage#LAST_USED_UNSET and LAST_USED_INVALID (patchset #1 id:1 of https://codereview.chromium.org/2927723003/ )

Reason for revert:
Spec revert due to significantly increased flakiness in one of the WebApkUpdateManagerTests: https://bugs.chromium.org/p/chromium/issues/detail?id=731485

Original issue's description:
> [Android Refactor] Merge WebappDataStorage#LAST_USED_UNSET and LAST_USED_INVALID
> 
> Having both LAST_USED_UNSET and LAST_USED_INVALID is unnecessary as
> - the "last_used" SharedPreference should never be set to LAST_USED_INVALID
> - there isn't any logic which checks whether "last_used" is LAST_USED_INVALID
> 
> Additionally, this CL renames LAST_USED_INVALID to TIMESTAMP_INVALID as
> the getters for several time-based SharedPreferences other than "last_used"
> return LAST_USED_INVALID if the preference is unset.
> 
> BUG=None
> 
> Review-Url: https://codereview.chromium.org/2927723003
> Cr-Commit-Position: refs/heads/master@{#478067}
> Committed: https://chromium.googlesource.com/chromium/src/+/618fd4f3564ecc43f4f7bff660c22a9dd5fc2309

TBR=dominickn@chromium.org,pkotwicz@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=None

Review-Url: https://codereview.chromium.org/2928993004
Cr-Commit-Position: refs/heads/master@{#478154}
Committed: https://chromium.googlesource.com/chromium/src/+/7fbcb3b02e0e1e1b3e42c46a4c0c0c1113357fdc

[jbudorick, 2017-06-09 01:24:52]

The CQ bit was checked by jbudorick@chromium.org

[jbudorick, 2017-06-09 01:24:52]

Created Revert of [Android Refactor] Merge WebappDataStorage#LAST_USED_UNSET and
LAST_USED_INVALID

[commit-bot: I haz the power, 2017-06-09 01:25:13]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-06-09 01:25:33]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1496971492282200, "parent_rev":
"28315859335578253ca195fb1a2fedb40889ae6b", "commit_rev":
"7fbcb3b02e0e1e1b3e42c46a4c0c0c1113357fdc"}

[commit-bot: I haz the power, 2017-06-09 01:25:45]

Description was changed from

==========
Revert of [Android Refactor] Merge WebappDataStorage#LAST_USED_UNSET and
LAST_USED_INVALID (patchset #1 id:1 of
https://codereview.chromium.org/2927723003/ )

Reason for revert:
Spec revert due to significantly increased flakiness in one of the
WebApkUpdateManagerTests:
https://bugs.chromium.org/p/chromium/issues/detail?id=731485

Original issue's description:
> [Android Refactor] Merge WebappDataStorage#LAST_USED_UNSET and
LAST_USED_INVALID
> 
> Having both LAST_USED_UNSET and LAST_USED_INVALID is unnecessary as
> - the "last_used" SharedPreference should never be set to LAST_USED_INVALID
> - there isn't any logic which checks whether "last_used" is LAST_USED_INVALID
> 
> Additionally, this CL renames LAST_USED_INVALID to TIMESTAMP_INVALID as
> the getters for several time-based SharedPreferences other than "last_used"
> return LAST_USED_INVALID if the preference is unset.
> 
> BUG=None
> 
> Review-Url: https://codereview.chromium.org/2927723003
> Cr-Commit-Position: refs/heads/master@{#478067}
> Committed:
https://chromium.googlesource.com/chromium/src/+/618fd4f3564ecc43f4f7bff660c2...

TBR=dominickn@chromium.org,pkotwicz@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=None
==========

to

==========
Revert of [Android Refactor] Merge WebappDataStorage#LAST_USED_UNSET and
LAST_USED_INVALID (patchset #1 id:1 of
https://codereview.chromium.org/2927723003/ )

Reason for revert:
Spec revert due to significantly increased flakiness in one of the
WebApkUpdateManagerTests:
https://bugs.chromium.org/p/chromium/issues/detail?id=731485

Original issue's description:
> [Android Refactor] Merge WebappDataStorage#LAST_USED_UNSET and
LAST_USED_INVALID
> 
> Having both LAST_USED_UNSET and LAST_USED_INVALID is unnecessary as
> - the "last_used" SharedPreference should never be set to LAST_USED_INVALID
> - there isn't any logic which checks whether "last_used" is LAST_USED_INVALID
> 
> Additionally, this CL renames LAST_USED_INVALID to TIMESTAMP_INVALID as
> the getters for several time-based SharedPreferences other than "last_used"
> return LAST_USED_INVALID if the preference is unset.
> 
> BUG=None
> 
> Review-Url: https://codereview.chromium.org/2927723003
> Cr-Commit-Position: refs/heads/master@{#478067}
> Committed:
https://chromium.googlesource.com/chromium/src/+/618fd4f3564ecc43f4f7bff660c2...

TBR=dominickn@chromium.org,pkotwicz@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=None

Review-Url: https://codereview.chromium.org/2928993004
Cr-Commit-Position: refs/heads/master@{#478154}
Committed:
https://chromium.googlesource.com/chromium/src/+/7fbcb3b02e0e1e1b3e42c46a4c0c...
==========

[commit-bot: I haz the power, 2017-06-09 01:25:47]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/7fbcb3b02e0e1e1b3e42c46a4c0c...