Fix "unused variable" warnings.

chrome/browser/signin/signin_status_metrics_provider_chromeos_unittest.cc

Index: chrome/browser/signin/signin_status_metrics_provider_chromeos_unittest.cc
diff --git a/chrome/browser/signin/signin_status_metrics_provider_chromeos_unittest.cc b/chrome/browser/signin/signin_status_metrics_provider_chromeos_unittest.cc
index 0a41d3bf48881567a7cafc973d9336950eb3397b..84c996a21ad526bd790c21b1bf2ab2abfdeb349e 100644
--- a/chrome/browser/signin/signin_status_metrics_provider_chromeos_unittest.cc
+++ b/chrome/browser/signin/signin_status_metrics_provider_chromeos_unittest.cc
@@ -10,8 +10,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 TEST(SigninStatusMetricsProviderChromeOS, ComputeSigninStatusToUpload) {
-  SigninStatusMetricsProviderChromeOS metrics_provider =
-      SigninStatusMetricsProviderChromeOS();
+  SigninStatusMetricsProviderChromeOS metrics_provider;

[Peter Kasting, 2016/05/19 05:11:37]

This was an interesting case.  The old code requires the copy constructor to be
accessible from this location, even though it's not actually called. 
SigninStatusMetricsProviderChromeOS uses DISALLOW_COPY_AND_ASSIGN, but the old
definition for that only makes that constructor private; since this test is a
friend, it can see that private declaration.  And since the copy constructor
isn't actually accessed, it doesn't matter that it's never defined.

Switching to "= delete" means the old code here won't compile.  Luckily, the fix
is easy.

 
   SigninStatusMetricsProviderBase::SigninStatus status_to_upload =
       metrics_provider.ComputeSigninStatusToUpload(