Componentize SSLErrorNavigationThrottle unittest

This CL follows up the componentization of SSLErrorNavigationThrottle
by componentizing its unittest. This involved disentangling the test
from //chrome dependencies, namely by constructing fakes of dependencies
internally rather than relying on //chrome for these dependencies. Note
that some of these dependencies will likely themselves be componentized
(notably, SSLBlockingPage); however, IMO it's still beneficial from a
separation-of-concerns POV to have the SSLErrorNavigationThrottle
unittest be decoupled from these other complex production classes.

Change-Id: I167b6caa263e77eb28b2cba95851128669ba8c71
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1917772
Commit-Queue: Colin Blundell <[email protected]>
Reviewed-by: Carlos IL <[email protected]>
Cr-Commit-Position: refs/heads/master@{#716581}
diff --git a/components/security_interstitials/content/BUILD.gn b/components/security_interstitials/content/BUILD.gn
index b7964a91..8b1f9d2 100644
--- a/components/security_interstitials/content/BUILD.gn
+++ b/components/security_interstitials/content/BUILD.gn
@@ -48,6 +48,7 @@
   testonly = true
   sources = [
     "security_interstitial_tab_helper_unittest.cc",
+    "ssl_error_navigation_throttle_unittest.cc",
   ]
 
   deps = [