[Extensions Cleanup] Move FeatureSwitch unittest

Move feature_switch_unittest.cc to //extensions to neighbor its
source file (feature_switch.[h|cc]). It has no //chrome dependencies.

Bug: None
Change-Id: Ie98bdd50d973e168e5ab593047fd697deec53bf2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2131626Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755415}

chrome/test/BUILD.gn

@@ -4761,7 +4761,6 @@ test("unit_tests") {
       "../common/extensions/chrome_manifest_url_handlers_unittest.cc",
       "../common/extensions/command_unittest.cc",
       "../common/extensions/extension_unittest.cc",
-      "../common/extensions/feature_switch_unittest.cc",
       "../common/extensions/manifest_handlers/app_display_mode_manifest_unittest.cc",
       "../common/extensions/manifest_handlers/app_theme_color_manifest_unittest.cc",
       "../common/extensions/manifest_handlers/automation_unittest.cc",

extensions/common/BUILD.gn

@@ -421,6 +421,7 @@ if (enable_extensions) {
       "extension_resource_unittest.cc",
       "extension_set_unittest.cc",
       "extension_unittest.cc",
+      "feature_switch_unittest.cc",
       "features/complex_feature_unittest.cc",
       "features/feature_provider_unittest.cc",
       "features/simple_feature_unittest.cc",

chrome/common/extensions/feature_switch_unittest.cc → extensions/common/feature_switch_unittest.cc

@@ -13,12 +13,13 @@ namespace {
 
 const char kSwitchName[] = "test-switch";
 
-template<FeatureSwitch::DefaultValue T>
+template <FeatureSwitch::DefaultValue T>
 class FeatureSwitchTest : public testing::Test {
  public:
   FeatureSwitchTest()
       : command_line_(base::CommandLine::NO_PROGRAM),
         feature_(&command_line_, kSwitchName, T) {}
+
  protected:
   base::CommandLine command_line_;
   FeatureSwitch feature_;