Merge multiple histogram snapshots into single one for reporting.

components/metrics/metrics_service_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/metrics/metrics_service.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 398 matching lines @@
   pma2.reset(base::HistogramBase::ReleaseDefaultPersistentMemoryAllocator());
 
   base::HistogramBase::SetDefaultPersistentMemoryAllocator(
       new base::LocalPersistentMemoryAllocator(64 << 10, std::string()));
 
   TestMetricsServiceClient client;
   TestMetricsService service(
       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);
     EXPECT_NE(service.persistent_end(), ++i);
     EXPECT_NE(service.persistent_end(), ++i);
     EXPECT_NE(service.persistent_end(), ++i);
     EXPECT_EQ(service.persistent_end(), ++i);
+    STLDeleteElements(&found);
   }
 }
 
 }  // namespace metrics