Added histograms on process singleton create when remote process exists and we cannot notify it

chrome/browser/process_singleton_posix_unittest.cc

Index: chrome/browser/process_singleton_posix_unittest.cc
diff --git a/chrome/browser/process_singleton_posix_unittest.cc b/chrome/browser/process_singleton_posix_unittest.cc
index 4c3922a030247d6d9f07d7a3089ecb010906a91d..e5217f29c63e193083ce73e06392fed6aa579bf4 100644
--- a/chrome/browser/process_singleton_posix_unittest.cc
+++ b/chrome/browser/process_singleton_posix_unittest.cc
@@ -27,6 +27,7 @@
 #include "base/single_thread_task_runner.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/test/histogram_tester.h"
 #include "base/test/test_timeouts.h"
 #include "base/test/thread_test_helper.h"
 #include "base/threading/thread.h"
@@ -286,12 +287,16 @@ TEST_F(ProcessSingletonPosixTest, NotifyOtherProcessSuccess) {
 
 // Test failure case of NotifyOtherProcess().
 TEST_F(ProcessSingletonPosixTest, NotifyOtherProcessFailure) {
+  base::HistogramTester histogram_tester;
   CreateProcessSingletonOnThread();
 
   BlockWorkerThread();
   EXPECT_EQ(ProcessSingleton::PROCESS_NONE, NotifyOtherProcess(true));
   ASSERT_EQ(1, kill_callbacks_);
   UnblockWorkerThread();
+  histogram_tester.ExpectUniqueSample(
+      "Chrome.ProcessSingleton.RemoteHungProcessTerminateReason",
+      ProcessSingleton::SOCKET_READ_FAILED, 1u);
 }
 
 // Test that we don't kill ourselves by accident if a lockfile with the same pid