Support "shared" histograms between processes.

chrome/service/service_ipc_server.cc

Index: chrome/service/service_ipc_server.cc
diff --git a/chrome/service/service_ipc_server.cc b/chrome/service/service_ipc_server.cc
index 869c4fbcd3de1e59aad2eacb04945590cb48c85e..de82ad09237f4903ef0d874275260fd749e42e7d 100644
--- a/chrome/service/service_ipc_server.cc
+++ b/chrome/service/service_ipc_server.cc
@@ -123,7 +123,10 @@ void ServiceIPCServer::OnGetHistograms() {
         new base::HistogramDeltaSerialization("ServiceProcess"));
   }
   std::vector<std::string> deltas;
-  histogram_delta_serializer_->PrepareAndSerializeDeltas(&deltas);
+  // "false" to PerpareAndSerializeDeltas() indicates to *not* include
+  // histograms held in persistent storage on the assumption that they will be
+  // visible to the recipient through other means.
+  histogram_delta_serializer_->PrepareAndSerializeDeltas(&deltas, false);
   channel_->Send(new ServiceHostMsg_Histograms(deltas));
 }