Enable SafeBrowsing

[jumde]

• Replace kSbV4UrlPrefix with the brave proxy
• Update the interstitial pages
• Disable reporting
• Update API key

Test Plan

1. Open brave and navigate to https://brave.com
2. Wait for 2-3 mins, and verify the *.store files have been created in <UserData>/Safe Browsing directory
3. Navigate to https://testsafebrowsing.appspot.com/ and verify that you see appropriate warnings for different demo pages.

[bbondy]

Is this issue fully completed?

[jumde]

API key update is tracked here: #543
Interstitial pages update is tracked here: #532

[btlechowski]

Verification passed on

Brave	0.55.5 Chromium: 70.0.3538.16 (Official Build) dev (64-bit)
Revision	16ed95b41bb05e565b11fb66ac33c660b721f778-refs/branch-heads/3538@{#306}
OS	Windows 7

Permissions Blacklisting does not work, but it also does not work in Chrome 69.0.3497.100

Verification Passed on

Brave	0.55.6 Chromium: 70.0.3538.16 (Official Build) dev (64-bit)
Revision	16ed95b41bb05e565b11fb66ac33c660b721f778-refs/branch-heads/3538@{#306}
OS	Linux

• Permission blocking works on Linux
  

Verified passed with

Brave	0.55.10 Chromium: 70.0.3538.22 (Official Build) beta(64-bit)
Revision	ac9418ba9c3bd7f6baaffa0b055dfe147e0f8364-refs/branch-heads/3538@{#468}
OS	Mac OS X