Support "shared" histograms between processes.

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 c4ed553029b10d4409bc84151bfb5b2d87ec38d4..03d810be3a7949634eb9414b67b871256c351df0 100644
--- a/components/metrics/metrics_service_unittest.cc
+++ b/components/metrics/metrics_service_unittest.cc
@@ -12,6 +12,8 @@
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/histogram_base.h"
+#include "base/metrics/histogram_persistence.h"
 #include "base/metrics/metrics_hashes.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/prefs/testing_pref_service.h"
@@ -397,4 +399,62 @@ TEST_F(MetricsServiceTest,
   EXPECT_TRUE(test_provider->on_recording_disabled_called());
 }
 
+TEST_F(MetricsServiceTest, MultiplePersistentAllocators) {
+  base::SetPersistentHistogramMemoryAllocator(
+      new base::LocalPersistentMemoryAllocator(64 << 10, 0, std::string()));
+  scoped_ptr<base::PersistentMemoryAllocator> pma1;
+  LOCAL_HISTOGRAM_COUNTS("MetricsServiceTest.MPA1A", 30);
+  LOCAL_HISTOGRAM_COUNTS("MetricsServiceTest.MPA1B", 30);
+  pma1.reset(base::ReleasePersistentHistogramMemoryAllocator());
+
+  base::SetPersistentHistogramMemoryAllocator(
+      new base::LocalPersistentMemoryAllocator(64 << 10, 0, std::string()));
+  scoped_ptr<base::PersistentMemoryAllocator> pma2;
+  LOCAL_HISTOGRAM_COUNTS("MetricsServiceTest.MPA2A", 30);
+  LOCAL_HISTOGRAM_COUNTS("MetricsServiceTest.MPA2B", 30);
+  LOCAL_HISTOGRAM_COUNTS("MetricsServiceTest.MPA2C", 30);
+  LOCAL_HISTOGRAM_COUNTS("MetricsServiceTest.MPA2D", 30);
+  pma2.reset(base::ReleasePersistentHistogramMemoryAllocator());
+
+  base::SetPersistentHistogramMemoryAllocator(
+      new base::LocalPersistentMemoryAllocator(64 << 10, 0, std::string()));
+
+  TestMetricsServiceClient client;
+  TestMetricsService service(
+      GetMetricsStateManager(), &client, GetLocalState());
+
+  {
+    MetricsService::PersistentHistogramIterator i = service.persistent_begin();
+    EXPECT_EQ(service.persistent_end(), i);
+  }
+
+  LOCAL_HISTOGRAM_COUNTS("MetricsServiceTest.MPA3A", 30);
+  {
+    MetricsService::PersistentHistogramIterator i = service.persistent_begin();
+    EXPECT_EQ(service.persistent_end(), i);
+  }
+
+  service.AddPersistentMemorySegment(pma1.get());
+  {
+    MetricsService::PersistentHistogramIterator i = service.persistent_begin();
+    EXPECT_NE(service.persistent_end(), i);
+    EXPECT_TRUE(*i);
+    EXPECT_NE(service.persistent_end(), ++i);
+    EXPECT_TRUE(*i);
+    EXPECT_EQ(service.persistent_end(), ++i);
+  }
+
+  service.AddPersistentMemorySegment(pma2.get());
+  {
+    MetricsService::PersistentHistogramIterator i = service.persistent_begin();
+    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);
+  }
+}
+
 }  // namespace metrics