Allow private tabs to set DDG as default search engine

[bbondy]

See how it works in browser-laptop for working spec.

Muon spec:
In private tab, user can turn on/off duckduckgo. If user turns it off, search engine of normal mode is used.
In tor enabled private tab, only duckduck can be used. User can't change it.

• Implement C++ modules and prefs for toggle different search engine
• Connect prefs with webui

[simonhong]

Search engine list is managed by TemplateURLService.
TemplateURLServiceFactory creates this service by using original profile.
That means incognito mode uses same service with normal mode.

To use different default search engine in incognito mode, incognito profile should be used by factory.

[srirambv]

Is this only the DDG search in incognito tab or will have a seperate section in chrome://settings/search to set it similar to b-l?

[GeetaSarvadnya]

Observations on Windows 10:

1. When user turn on DDG in private tab, search engine is using DDG
2. When user turn on DDG in private tab, click on Refresh button is making DDG off @srirambv already logged an issue Reload new incognito tab resets DDG search button #1235.
3. In Tor enabled private tab, search engine is NOT DDG, its still using google.
   Tor window uses Google.com by default #1226.
4. On Fresh profile, when user is on chrome://welcome screen, click on user icon -> "Open Tor Window" option is not available. Open new tab and come back to chrome://welcome and see "Open Tor Window" option in user pop up. @srirambv this was identified by you, i didn't find defect ID please add defect id here.

[srirambv]

@GeetaSarvadnya step 4 is not an issue. Its just delay in downloading the Tor binaries which makes it not list it on the welcome tab. If you wait till the Tor binaries are downloaded it will show option on the welcome screen itself.

[simonhong]

Is this only the DDG search in incognito tab or will have a separate section in chrome://settings/search to set it similar to b-l?

This issue was only for making DDG toggle button work in private tab.
If we want to have a separate toggle option in settings like b-l, I think new issue should track about it(if it isn't existed yet).
@srirambv

[srirambv]

Thanks for the update @simonhong . #1186 is logged for separate search settings.

[srirambv]

QA Blocked on #1186

[srirambv]

Verification Passed on

Brave	0.55.14 Chromium: 70.0.3538.54 (Official Build) beta(64-bit)
Revision	4f8e578b6680574714e9ed3bb9f02922b4dde40d-refs/branch-heads/3538@{#937}
OS	Linux

• Based on Allow private tabs to set DDG as default search engine #61 (comment), verified DDG is set as default search engine when the DDG switch is toggled

Verified passed with

Brave	0.55.14 Chromium: 70.0.3538.54 (Official Build) beta(64-bit)
Revision	4f8e578b6680574714e9ed3bb9f02922b4dde40d-refs/branch-heads/3538@{#937}
OS	Mac OS X

• Based on Allow private tabs to set DDG as default search engine #61 (comment), verified DDG is set as default search engine when the DDG switch is toggled

Verification passed on

Brave	0.55.14 Chromium: 70.0.3538.54 (Official Build) beta(64-bit)
Revision	4f8e578b6680574714e9ed3bb9f02922b4dde40d-refs/branch-heads/3538@{#937}
OS	Windows 7