components: Cleanup class/struct fwd declarations

components/component_updater/component_updater_service.h

Index: components/component_updater/component_updater_service.h
diff --git a/components/component_updater/component_updater_service.h b/components/component_updater/component_updater_service.h
index 72bc13d2865b7e9615fa25a22d75081f7167d187..38961e2ec3e25428cd46ab82d12875948b729c48 100644
--- a/components/component_updater/component_updater_service.h
+++ b/components/component_updater/component_updater_service.h
@@ -20,23 +20,11 @@
 
 class ComponentsUI;
 class PluginObserver;
-class SupervisedUserWhitelistService;
 
 namespace base {
-class DictionaryValue;
-class FilePath;
 class SequencedTaskRunner;
 }
 
-namespace content {
-class ResourceThrottle;
-}
-
-namespace net {
-class URLRequestContextGetter;
-class URLRequest;
-}
-
 namespace policy {
 class ComponentUpdaterPolicyTest;
 }