crashpad: Pass --always_allow_feedback during tests

On ChromeOS, pass --always_allow_feedback when running unattended
(during integration tests). This avoids the need for most tests to try
and set metrics consent.

Requires https://chromium-review.googlesource.com/c/crashpad/crashpad/+/1981037 to be rolled into Chromium before checkin.

BUG=chromium:1037656
TEST=tast -verbose run --extrauseflags chrome_internal my_crbook ui.ChromeCrashNotLoggedInDirect

Change-Id: I7ba481286c87856f2d5e8cebf224b9b1b6212824
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1981139
Commit-Queue: Ian Barkley-Yeung <iby@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Auto-Submit: Ian Barkley-Yeung <iby@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728667}

components/crash/content/app/crashpad_linux.cc

@@ -163,6 +163,7 @@ base::FilePath PlatformCrashpadInitialization(
     if (crash_reporter_client->IsRunningUnattended()) {
       arguments.push_back(base::StringPrintf("--minidump-dir-for-tests=%s",
                                              database_path.value().c_str()));
+      arguments.push_back("--always-allow-feedback");
     }
 #endif