Merge multiple histogram snapshots into single one for reporting.

components/metrics/metrics_service_unittest.cc

Index: components/metrics/metrics_service_unittest.cc
diff --git a/components/metrics/metrics_service_unittest.cc b/components/metrics/metrics_service_unittest.cc
index c6c5794546d85e792d6181b9fe4c151115cc55df..50fc91c41477622810fe55d29b3816039c52c7c4 100644
--- a/components/metrics/metrics_service_unittest.cc
+++ b/components/metrics/metrics_service_unittest.cc
@@ -416,29 +416,40 @@ TEST_F(MetricsServiceTest, MultiplePersistentAllocators) {
       GetMetricsStateManager(), &client, GetLocalState());
 
   {
-    MetricsService::PersistentHistogramIterator i = service.persistent_begin();
+    MetricsService::HistogramSet found;
+    MetricsService::PersistentHistogramIterator i =
+        service.persistent_begin(&found);
     EXPECT_EQ(service.persistent_end(), i);
+    STLDeleteElements(&found);
   }
 
   LOCAL_HISTOGRAM_COUNTS("MetricsServiceTest.MPA3A", 30);
   {
-    MetricsService::PersistentHistogramIterator i = service.persistent_begin();
+    MetricsService::HistogramSet found;
+    MetricsService::PersistentHistogramIterator i =
+        service.persistent_begin(&found);
     EXPECT_EQ(service.persistent_end(), i);
+    STLDeleteElements(&found);

[Alexei Svitkine (slow), 2015/12/04 18:30:11]

Can HistogramSet have scoped_ptrs as members, so this wouldn't be necessary?
Otherwise, it's too easy to leak using the API.

[bcwhite, 2015/12/08 17:32:18]

Yes, though it makes it impossible do do some things due to the fact that it's
the key.  For example, you can't find() to see if an entry already exists.  This
breaks the existing DCHECK to ensure we don't double-insert a histogram.

HistogramSet is private (well, will be shortly) to MetricsService so I'm not
sure which approach is best here.

   }
 
   service.AddPersistentMemorySegment(pma1.get());
   {
-    MetricsService::PersistentHistogramIterator i = service.persistent_begin();
+    MetricsService::HistogramSet found;
+    MetricsService::PersistentHistogramIterator i =
+        service.persistent_begin(&found);
     EXPECT_NE(service.persistent_end(), i);
     EXPECT_TRUE(*i);
     EXPECT_NE(service.persistent_end(), ++i);
     EXPECT_TRUE(*i);
     EXPECT_EQ(service.persistent_end(), ++i);
+    STLDeleteElements(&found);
   }
 
   service.AddPersistentMemorySegment(pma2.get());
   {
-    MetricsService::PersistentHistogramIterator i = service.persistent_begin();
+    MetricsService::HistogramSet found;
+    MetricsService::PersistentHistogramIterator i =
+        service.persistent_begin(&found);
     EXPECT_NE(service.persistent_end(), i);
     EXPECT_NE(service.persistent_end(), ++i);
     EXPECT_NE(service.persistent_end(), ++i);
@@ -446,6 +457,7 @@ TEST_F(MetricsServiceTest, MultiplePersistentAllocators) {
     EXPECT_NE(service.persistent_end(), ++i);
     EXPECT_NE(service.persistent_end(), ++i);
     EXPECT_EQ(service.persistent_end(), ++i);
+    STLDeleteElements(&found);
   }
 }