Add validation error messages to network CSP parser

The Content-Security-Policy parser in services/network was silently
ignoring all parsing errors. This is not an issue, since CSPs are
being parsed again in blink, where errors are reported to the
console. However, after we bring CSPEE out-of-blink, the frame csp
attribute will not be parsed in blink anymore, so we will need
validation from the network CSP parser. This change implements it.

Bug: 1094909
Change-Id: I38e572900afcc9a4e55148e206690a16345cd99a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2279976Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Commit-Queue: Antonio Sartori <antoniosartori@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789412}

services/network/public/cpp/BUILD.gn

@@ -131,6 +131,7 @@ jumbo_component("cpp") {
 
   deps = [
     "//base",
+    "//base/util/ranges:ranges",
     "//components/prefs",
     "//ipc",
     "//services/proxy_resolver/public/mojom",

services/network/public/mojom/content_security_policy.mojom

@@ -149,6 +149,9 @@ struct ContentSecurityPolicy {
 
   // Set of reporting endpoints to which violation reports are sent.
   array<string> report_endpoints;
+
+  // An array containing a set of errors occurred while parsing the CSP header.
+  array<string> parsing_errors;
 };
 
 // Data to report Content-Security-Policy violations.