handle empty objects in sync DELETEs, refactor DELETE code

[diracdeltas]

fix #9308
gets rid of syncActions.removeSite by DELETEing sites in the appStoreChange listener instead

test plan:

1. enable sync in pyramid 0.
2. bookmark some sites and folders and then delete some.
3. sync pyramid 1 to pyramid 0. it should show the same bookmarks.
4. delete a bookmark and bookmark folder in pyramid 1. they should be deleted in pyramid 0.
5. syncing tests should pass.

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.

Test Plan:

Reviewer Checklist:

Tests

• Adequate test coverage exists to prevent regressions
• Tests should be independent and work correctly when run individually or as a suite ref
• New files have MPL2 license header

[ayumi]

i'm having mild issues testing this right now because i can't delete bookmarks (right click menu doesn't work on toolbar or bookmarks manager)

[diracdeltas]

@ayumi same; i worked around it by going to the site and clicking on the bookmark star to edit it. doesn't work for deleting bookmark folders though.

[diracdeltas]

@ayumi fixed by rebase

[ayumi]

I get an error when sync is enabled and i try to delete a bookmark toolbar bookmark or folder:

sync 1497298899503: sending record: {"action":0,"bookmark":{"hideInToolbar":false,"isFolder":false,"site":{"creationTime":0,"customTitle":"","favicon":"","lastAccessedTime":0,"location":"https://archive.org/","title":"Internet Archive: Digital Library of Free Books, Movies, Music & Wayback Machine"}},"deviceId":{"0":0},"objectId":{"0":88,"1":27,"2":9,"3":5,"4":193,"5":163,"6":63,"7":17,"8":32,"9":20,"10":19,"11":60,"12":194,"13":251,"14":248,"15":199}}
An uncaught exception occurred in the main process Uncaught Exception:
AssertionError: state must be an Immutable.Map
    at validateState (/repos/github.com/brave/browser-laptop/app/common/state/windowState.js:18:10)
    at Object.getActiveWindow (/repos/github.com/brave/browser-laptop/app/common/state/windowState.js:75:13)
    at Object.getActiveWindowId (/repos/github.com/brave/browser-laptop/app/common/state/windowState.js:80:21)
    at Object.getActiveTab (/repos/github.com/brave/browser-laptop/app/common/state/tabState.js:543:48)
    at updateActiveTabBookmarked (/repos/github.com/brave/browser-laptop/app/browser/reducers/sitesReducer.js:32:24)
    at sitesReducer (/repos/github.com/brave/browser-laptop/app/browser/reducers/sitesReducer.js:85:15)

STR:

1. Fresh profile; enable sync.
2. Add folder to bookmark toolbar
3. Try to delete the folder from the toolbar

[ayumi]

is this no longer needed?

[diracdeltas]

correct

[diracdeltas]

@ayumi that error should be fixed now

[ayumi]

⚗

[diracdeltas]

https://travis-ci.org/brave/browser-laptop/jobs/242177590 shows 1 test failure but it passes locally so seems unrelated

[bsclifton]

@diracdeltas don't forget to cherry-pick into 0.18.x now that master is pointing at 0.19.x 😄

[diracdeltas]

@bsclifton cool, i will do that once the fixes for this PR are approved (#9407)

[diracdeltas]

this is causing weird behavior with moving sites. may have to revert.