[Clean up] Move VariationsHttpHeaderProvider into a subdirectory.

components/variations/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
-static_library("variations") {
+source_set("variations") {
   sources = [
     "active_field_trials.cc",
     "active_field_trials.h",
     "android/component_jni_registrar.cc",
     "android/component_jni_registrar.h",
     "android/variations_associated_data_android.cc",
     "android/variations_associated_data_android.h",
     "caching_permuted_entropy_provider.cc",
     "caching_permuted_entropy_provider.h",
     "entropy_provider.cc",
     "entropy_provider.h",
     "metrics_util.cc",
     "metrics_util.h",
     "pref_names.cc",
     "pref_names.h",
     "processed_study.cc",
     "processed_study.h",
     "proto/client_variations.proto",
     "proto/permuted_entropy_cache.proto",
     "proto/study.proto",
     "proto/variations_seed.proto",
     "study_filtering.cc",
     "study_filtering.h",
     "variations_associated_data.cc",
     "variations_associated_data.h",
-    "variations_http_header_provider.cc",
-    "variations_http_header_provider.h",
     "variations_seed_processor.cc",
     "variations_seed_processor.h",
     "variations_seed_simulator.cc",
     "variations_seed_simulator.h",
   ]
 
   deps = [
+    "proto",
     "//base",
-    "//components/variations/proto",
     "//third_party/mt19937ar",
   ]
 
   if (is_android) {
     deps += [ ":jni" ]
   }
 }
 
 if (is_android) {
   # GYP: //components/variations.gypi:variations_jni_headers
   generate_jni("jni") {
     sources = [
       "android/java/src/org/chromium/components/variations/VariationsAssociatedData.java",
     ]
     jni_package = "variations"
   }
 }
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "active_field_trials_unittest.cc",
+    "caching_permuted_entropy_provider_unittest.cc",
+    "entropy_provider_unittest.cc",
+    "metrics_util_unittest.cc",
+    "net/variations_http_header_provider_unittest.cc",
+    "study_filtering_unittest.cc",
+    "variations_associated_data_unittest.cc",
+    "variations_seed_processor_unittest.cc",
+    "variations_seed_simulator_unittest.cc",
+  ]
+
+  deps = [
+    ":variations",
+    "net",
+    "proto",
+    "//base/test:test_support",
+    "//testing/gtest",
+  ]
+}