Create ForTesting method rather than declaring a dozen "friend" classes.

chrome/browser/metrics/subprocess_metrics_provider_unittest.cc

Index: chrome/browser/metrics/subprocess_metrics_provider_unittest.cc
diff --git a/chrome/browser/metrics/subprocess_metrics_provider_unittest.cc b/chrome/browser/metrics/subprocess_metrics_provider_unittest.cc
index 43f697ee7298484d25acbda83c9adb187b30b955..4f3779c68a80670173cb0fc8db0797384da56258 100644
--- a/chrome/browser/metrics/subprocess_metrics_provider_unittest.cc
+++ b/chrome/browser/metrics/subprocess_metrics_provider_unittest.cc
@@ -67,7 +67,7 @@ class SubprocessMetricsProviderTest : public testing::Test {
     provider_.MergeHistogramDeltas();
 
     // Create a dedicated StatisticsRecorder for this test.
-    test_recorder_.reset(new base::StatisticsRecorder());
+    test_recorder_ = base::StatisticsRecorder::CreateTemporaryForTesting();
 
     // Create a global allocator using a block of memory from the heap.
     base::GlobalHistogramAllocator::CreateWithLocalMemory(TEST_MEMORY_SIZE,