Reland #2: Eliminate browser test helpers from unit tests.

This change eliminates dependencies of browser_test_utils.h and
in_process_browser_test.h from unit tests and eliminates the future
possibility of adding them back by changing gn and gyp configurations.

This also renames one test from "unit" to "browser" as it seems more
appropriate for the case.

Revert CL: http://crbug.com/1658733002
Reverted CL: http://crbug.com/1613123002

BUG=514788
[email protected]

Review URL: https://codereview.chromium.org/1659843002

Cr-Commit-Position: refs/heads/master@{#372941}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 47f1ce02..20339d3 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -1142,6 +1142,7 @@
     "//components/search_engines:test_support",
     "//components/syncable_prefs:test_support",
     "//components/user_prefs/tracked:user_prefs_tracked_test_support",
+    "//content/test:browsertest_base",
     "//content/test:test_support",
     "//net:test_support",
     "//skia",