Disable Reporting API

[pes10k]

Chromium includes a system called Reporting API. Its a broad API that is currently used to allow sites to instruct the browser to send at least the following types of information (possibly others) to arbitrary parties (i.e. first or 3p):

• CSP errors
• Network errors
• Interventions (e.g. webRequest blocked something)
• Crash reports

Most of the functionality is all defined though HTTP headers, though there is a JS API that allows the site to see and edit reports as they go out).

There is a compile time flag to disable Reporting API. We should do this. Of the functionality that goes through Reporting API, two have possible use cases (CSP and crash reports, though Brave opinions differ on whether they're user-respecting to have on by default), and two are clearly privacy harming (network error reporting, that is a clear tracking vector, and intervention reporting, which is obviously horrible).

Regardless of whether we decide to enable CSP and crash reports, there won't be resources to do so for a while. There is an "easy" way to disable the entire "parent" API (reporting API). We should do so ASAP, until there are resources to possibly re-enable the non-privacy harming parts.

Information about Reporting API

• Google Explainer
• Proposed Spec

Test Plan

Specified here: brave/brave-core#4578

[LaurenWags]

Verified passed with

Brave	1.7.66 Chromium: 80.0.3987.149 (Official Build) dev (64-bit)
Revision	5f4eb224680e5d7dca88504586e9fd951840cac6-refs/branch-heads/3987_137@{#16}
OS	macOS Version 10.14.6 (Build 18G3020)

• Confirmed test plan from Fix 7956: Disable reporting observers to expose violation reports to JS brave-core#4578 - visited https://jumde.github.io/test/reporting_observer.html and confirmed Reporting Observers not available does display using 1.7.x.

• Also visited https://jumde.github.io/test/reporting_observer.html using 1.5.113 and confirmed Reporting Observers not available message does not display using 1.5.113.

Verification passed on

Brave	1.7.67 Chromium: 80.0.3987.149 (Official Build) beta (64-bit)
Revision	5f4eb224680e5d7dca88504586e9fd951840cac6-refs/branch-heads/3987_137@{#16}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Confirmed test plan from Fix 7956: Disable reporting observers to expose violation reports to JS brave-core#4578 - visited https://jumde.github.io/test/reporting_observer.html and confirmed Reporting Observers not available does display using 1.7.x.
  

• Also visited https://jumde.github.io/test/reporting_observer.html using 1.5.113 and confirmed Reporting Observers not available message does not display using 1.5.113.
  

Verification passed on

Brave	1.7.70 Chromium: 80.0.3987.149 (Official Build) dev (64-bit)
Revision	5f4eb224680e5d7dca88504586e9fd951840cac6-refs/branch-heads/3987_137@{#16}
OS	Ubuntu 18.04 LTS