User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:75.0) Gecko/20100101 Firefox/75.0

Steps to reproduce:

Go to any websites, click on the URL bar and delete or backspace until the URL bar is empty. Notice that when the URL bar is empty, the top sites dropdown list closes even though the URL bar is still focused. I don't think this behaviour is right. I think the top sites list should remain open (the URL bar is still focused...).

Expected results:

I understand behaviours like this are subjective but this one really sticks out to me as wrong, please consider changing it. Maybe this is even worth making an experiment!

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

I agree. We should continue to show top sites when the url has been deleted. This will also prevent the flicker of the dropdown closing and then reopening if you start typing a search.

Not sure whether this should be part of update-1 or update-2, let's assume -1 for now considered we have the 75 cycle.
P3 as a nice-to-have.
Verdi, if this should be a blocker please let us know.

Push with failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&group_state=expanded&resultStatus=testfailed%2Cbusted%2Cexception&revision=c496f46b0a15edb776ab331e772ef4685501ffde&selectedJob=290636648

Failure log: https://treeherder.mozilla.org/logviewer.html#?job_id=290636648&repo=autoland

Backout link: https://hg.mozilla.org/integration/autoland/rev/0ccb086289a118f41a3a18f81e4c90dc963eae72

[task 2020-02-26T20:06:14.285Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Check urlbar value - "In" == "In" -
[task 2020-02-26T20:06:14.285Z] 20:06:14 INFO - If all characters are removed, the popup should be closed.
[task 2020-02-26T20:06:14.285Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Popup should be open - true == true -
[task 2020-02-26T20:06:14.286Z] 20:06:14 INFO - Buffered messages finished
[task 2020-02-26T20:06:14.286Z] 20:06:14 INFO - TEST-UNEXPECTED-FAIL | browser/components/urlbar/tests/browser/browser_ime_composition.js | Test timed out -
[task 2020-02-26T20:06:14.287Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Check urlbar value - "" == "" -
[task 2020-02-26T20:06:14.287Z] 20:06:14 INFO - Composition which is canceled shouldn't cause opening the popup.
[task 2020-02-26T20:06:14.288Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Popup should be closed - true == true -
[task 2020-02-26T20:06:14.289Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Popup should be closed - true == true -
[task 2020-02-26T20:06:14.289Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Check urlbar value - "I" == "I" -
[task 2020-02-26T20:06:14.290Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Popup should be closed - true == true -
[task 2020-02-26T20:06:14.296Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Check urlbar value - "In" == "In" -
[task 2020-02-26T20:06:14.296Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Popup should be closed - true == true -
[task 2020-02-26T20:06:14.296Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Check urlbar value - "" == "" -
[task 2020-02-26T20:06:14.297Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Popup should be closed - true == true -
[task 2020-02-26T20:06:14.297Z] 20:06:14 INFO - TEST-PASS | browser/components/urlbar/tests/browser/browser_ime_composition.js | Check urlbar value - "" == "" -
[task 2020-02-26T20:06:14.298Z] 20:06:14 INFO - Down key should open the popup even if the editor is empty.
[task 2020-02-26T20:06:14.298Z] 20:06:14 INFO - GECKO(3810) | MEMORY STAT | vsize 3258MB | residentFast 403MB | heapAllocated 133MB
[task 2020-02-26T20:06:14.299Z] 20:06:14 INFO - TEST-OK | browser/components/urlbar/tests/browser/browser_ime_composition.js | took 90135ms
[task 2020-02-26T20:06:14.301Z] 20:06:14 INFO - GECKO(3810) | [Child 3991: Main Thread]: I/DocShellAndDOMWindowLeak ++DOCSHELL 0x7fda78f16800 == 1 [pid = 3991] [id = {6b772b9f-337f-4577-889c-f0ef58c6062f}]
[task 2020-02-26T20:06:14.301Z] 20:06:14 INFO - GECKO(3810) | [Child 3991: Main Thread]: I/DocShellAndDOMWindowLeak ++DOMWINDOW == 1 (0x7fda792a9090) [pid = 3991] [serial = 64] [outer = (nil)]
[task 2020-02-26T20:06:14.302Z] 20:06:14 INFO - GECKO(3810) | [Child 3991, Main Thread] WARNING: NS_ENSURE_TRUE(mPresShell) failed: file /builds/worker/workspace/build/src/layout/base/nsPresContext.cpp, line 848
[task 2020-02-26T20:06:14.302Z] 20:06:14 INFO - GECKO(3810) | [Child 3991: Main Thread]: I/DocShellAndDOMWindowLeak ++DOMWINDOW == 2 (0x7fda79256400) [pid = 3991] [serial = 65] [outer = 0x7fda792a9090]
[task 2020-02-26T20:06:14.302Z] 20:06:14 INFO - checking window state
[task 2020-02-26T20:06:14.303Z] 20:06:14 INFO - TEST-START | browser/components/urlbar/tests/browser/browser_inputHistory.js
[task 2020-02-26T20:06:14.340Z] 20:06:14 INFO - GECKO(3810) | [Parent 3810, Main Thread] WARNING: Suboptimal indexes for the SQL statement 0x7f1f42262b40 (http://mzl.la/1FuID0j).: file /builds/worker/workspace/build/src/storage/mozStoragePrivateHelpers.cpp, line 106
[task 2020-02-26T20:06:14.749Z] 20:06:14 INFO - Not taking screenshot here: see the one that was previously logged
[task 2020-02-26T20:06:14.750Z] 20:06:14 INFO - Buffered messages logged at 20:06:14
[task 2020-02-26T20:06:14.751Z] 20:06:14 INFO - Entering test bound setup
[task 2020-02-26T20:06:14.751Z] 20:06:14 INFO - Leaving test bound setup
[task 2020-02-26T20:06:14.751Z] 20:06:14 INFO - Entering test bound test_adaptive_no_search_terms
[task 2020-02-26T20:06:14.751Z] 20:06:14 INFO - Same visit count, different picks
[task 2020-02-26T20:06:14.752Z] 20:06:14 INFO - Buffered messages finished
[task 2020-02-26T20:06:14.753Z] 20:06:14 INFO - TEST-UNEXPECTED-FAIL | browser/components/urlbar/tests/browser/browser_ime_composition.js | Uncaught exception received from previously timed out test - at chrome://mochitests/content/browser/browser/components/urlbar/tests/browser/browser_ime_composition.js:133 - TypeError: can't access property "equal", Assert is null
[task 2020-02-26T20:06:14.754Z] 20:06:14 INFO - Stack trace:
[task 2020-02-26T20:06:14.754Z] 20:06:14 INFO - test_composition@chrome://mochitests/content/browser/browser/components/urlbar/tests/browser/browser_ime_composition.js:133:3
[task 2020-02-26T20:06:14.755Z] 20:06:14 INFO - Async*Tester_execTest/<@chrome://mochikit/content/browser-test.js:1062:34
[task 2020-02-26T20:06:14.755Z] 20:06:14 INFO - Tester_execTest@chrome://mochikit/content/browser-test.js:1097:11
[task 2020-02-26T20:06:14.755Z] 20:06:14 INFO - nextTest/<@chrome://mochikit/content/browser-test.js:925:14
[task 2020-02-26T20:06:14.755Z] 20:06:14 INFO - SimpleTest.waitForFocus/waitForFocusInner/focusedOrLoaded/<@chrome://mochikit/content/tests/SimpleTest/SimpleTest.js:914:23

https://hg.mozilla.org/mozilla-central/rev/ab4bd6ec708f