Fix overlay bug when offline

[wu-hui]

Fix: #3528

[google-oss-bot]

Coverage Report ¹

Affected Products

• firebase-firestore

  Overall coverage changed from 45.63% (f5845b2) to 45.66% (834eec2) by +0.03%.

  Filename	Base (f5845b2)	Merge (834eec2)	Diff
  AsyncQueue.java	77.11%	78.11%	+1.00%
  LocalStore.java	99.35%	99.37%	+0.02%
  MutationBatch.java	89.06%	89.23%	+0.17%
  PatchMutation.java	100.00%	98.39%	-1.61%

Test Logs

• Base (f5845b2): https://android-ci.firebaseopensource.com/view/gcs/android-ci/logs/postsubmit-check-coverage/1503790629769973761
• Merge (834eec2): https://android-ci.firebaseopensource.com/view/gcs/android-ci/pr-logs/pull/firebase_firebase-android-sdk/3537/check-coverage-changed/1503850525077016578

Notes

• Commit (834eec2) is created by Prow via merging PR base commit (f5845b2) and head commit (0ff7ae7).
• Run gradle <product>:checkCoverage to produce HTML coverage reports locally. After gradle commands finished, report files can be found under <product-build-dir>/reports/jacoco/.

1. https://storage.googleapis.com/firebase-sdk-metric-reports/D4i3gvE32s.html

[google-oss-bot]

Size Report ¹

Affected Products

• firebase-firestore

  Type	Base (f5845b2)	Merge (834eec2)	Diff
  aar	1.24 MB	1.24 MB	+333 B (+0.0%)
  apk (release)	3.38 MB	3.38 MB	-272 B (-0.0%)

Test Logs

• Base (f5845b2): https://android-ci.firebaseopensource.com/view/gcs/android-ci/logs/postsubmit-binary-size/1503790629769973763
• Merge (834eec2): https://android-ci.firebaseopensource.com/view/gcs/android-ci/pr-logs/pull/firebase_firebase-android-sdk/3537/binary-size/1503850525077016583

Notes

• Commit (834eec2) is created by Prow via merging PR base commit (f5845b2) and head commit (0ff7ae7).

1. https://storage.googleapis.com/firebase-sdk-metric-reports/TsujZH8Sqk.html

[dconeybe]

This PR needs a change log entry. Also, please apply the feedback from @schmidt-sebastian, if any.

[schmidt-sebastian]

Thanks

[google-oss-bot]

@wu-hui: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
smoke-tests	0ff7ae7	link	/test smoke-tests

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[wu-hui]

This PR needs a change log entry. Also, please apply the feedback from @schmidt-sebastian, if any.

Done.