Performance : urlbar response is slow when searching across many bookmarks

[alexwykoff]

Test plan

#8824 (comment)

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• Did you search for similar issues before submitting this one?
  Yes

• Describe the issue you encountered:
  After importing a large number of bookmarks, the urlbar response becomes considerably slow. It was found that bookmarks suggestions was the controlling factor.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Tested on OS X

• Brave Version (revision SHA):
  0.13.5 (0e68342)

• Steps to reproduce:

  1. With a clean session, try to visit reddit.com, add a couple bookmarks
  2. Import a large number of bookmarks
  3. With a new tab, try to visit reddit.com

• Actual result:
  The urlbar becomes considerably laggy.

• Expected result:
  The urlbar should be at least as responsive as if the bookmarks were not there. That is, a user should not be penalized for trying to visit a domain root when they have bookmarks to deeper links.

• Will the steps above reproduce in a fresh profile? If not what other info can be added?
  Yes

• Is this an issue in the currently released version?
  Yes

• Can this issue be consistently reproduced?
  Yes

• Extra QA steps:
  1.
  2.
  3.

• Screenshot if needed:

2017-03-02 09-52-15.mp4.zip

• Any related issues:

[scottbroadway]

Agree -- I'm seeing this. Painful.

0.13.5 rev 1db81cb on Windows x64

[cndouglas]

+1 from #6620.

[ayumi]

+1 #8643

[cndouglas]

Moving assignment from #8643.