Add UMA for PurgeAndSuspend.

content/child/child_discardable_shared_memory_manager.cc

Index: content/child/child_discardable_shared_memory_manager.cc
diff --git a/content/child/child_discardable_shared_memory_manager.cc b/content/child/child_discardable_shared_memory_manager.cc
index 44384491f1d4e739dadbe8a3851352bb11dc7bb0..1d1aa4c4591f0ba2aaacf3050aeb3e08ba6c4dc4 100644
--- a/content/child/child_discardable_shared_memory_manager.cc
+++ b/content/child/child_discardable_shared_memory_manager.cc
@@ -235,6 +235,15 @@ bool ChildDiscardableSharedMemoryManager::OnMemoryDump(
   return heap_.OnMemoryDump(pmd);
 }
 
+ChildDiscardableSharedMemoryManager::Statistics
+ChildDiscardableSharedMemoryManager::GetStatistics() const {
+  base::AutoLock lock(lock_);
+  Statistics stats;
+  stats.total_size = heap_.GetSize();
+  stats.freelist_size = heap_.GetSizeOfFreeLists();
+  return stats;
+}
+
 void ChildDiscardableSharedMemoryManager::ReleaseFreeMemory() {
   base::AutoLock lock(lock_);