Revert of Remove unneeded Friend from chrome_metrics_service_accessor...

Revert of Remove unneeded Friend from chrome_metrics_service_accessor (patchset #1 id:20001 of https://codereview.chromium.org/601243002/)

Reason for revert:
We need to bring this back since the usage of it is coming back in an upcoming patch.

Sorry about that...

BYE
MAD

Original issue's description:
> Remove unneeded Friend from chrome_metrics_service_accessor
>
> BUG=
>
> Committed: https://crrev.com/ca032c3aed93e5afd7c32da76147f36a72dc4341
> Cr-Commit-Position: refs/heads/master@{#296722}

TBR=asvitkine@chromium.org,csharp@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/603173003

Cr-Commit-Position: refs/heads/master@{#296763}

chrome/browser/metrics/chrome_metrics_service_accessor.h

@@ -14,6 +14,7 @@
 #include "chrome/browser/metrics/metrics_service_accessor.h"
 
 class ChromeExtensionDownloaderFactory;
+class PrefService;
 class Profile;
 
 namespace {
@@ -21,6 +22,12 @@ class CrashesDOMHandler;
 class FlashDOMHandler;
 }
 
+namespace component_updater {
+class ComponentUpdateService;
+void RegisterSwReporterComponent(ComponentUpdateService* cus,
+                                 PrefService* prefs);
+}
+
 namespace extensions {
 class MetricsPrivateGetIsCrashReportingEnabledFunction;
 }
@@ -42,6 +49,9 @@ class BrowserOptionsHandler;
 // as a 'friend' below.
 class ChromeMetricsServiceAccessor : public MetricsServiceAccessor {
  private:
+  friend void component_updater::RegisterSwReporterComponent(
+      component_updater::ComponentUpdateService* cus,
+      PrefService* prefs);
   friend bool prerender::IsOmniboxEnabled(Profile* profile);
   friend class ChromeExtensionDownloaderFactory;
   friend class ChromeRenderMessageFilter;