Adding UMA to track previews opt outs and blacklist eligibility

components/previews/core/BUILD.gn

Index: components/previews/core/BUILD.gn
diff --git a/components/previews/core/BUILD.gn b/components/previews/core/BUILD.gn
index 253d762624f60f8a10b8e07538714b16a468c093..92ae912fb4feb2b366b0b8d8d32375872a74f1b6 100644
--- a/components/previews/core/BUILD.gn
+++ b/components/previews/core/BUILD.gn
@@ -26,7 +26,7 @@ static_library("core") {
     "//base",
     "//components/data_reduction_proxy/core/common",
     "//components/variations",
-    "//net",
+    "//net:net",
     "//sql",
     "//url:url",
   ]
@@ -50,6 +50,8 @@ source_set("unit_tests") {
     "//base/test:test_support",
     "//components/data_reduction_proxy/core/common",
     "//components/variations",
+    "//net:net",
+    "//net:test_support",
     "//sql",
     "//sql:test_support",
     "//testing/gtest",