[Tentaive patch for discussion] Add Purge+Suspend metrics as UMA.

content/public/common/content_features.cc

Index: content/public/common/content_features.cc
diff --git a/content/public/common/content_features.cc b/content/public/common/content_features.cc
index d5445734b78496923b66e6d332a33d60c9172082..dec78118e12b200bf86474f68479845ba685334b 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -124,6 +124,10 @@ const base::Feature kPointerEvents{"PointerEvent",
 const base::Feature kPointerEventV1SpecCapturing{
     "PointerEventV1SpecCapturing", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Purge and suspend for background renderers.
+const base::Feature kPurgeAndSuspend{"PurgeAndSuspend",
+                                     base::FEATURE_DISABLED_BY_DEFAULT};
+
 // RAF aligned input events support.
 const base::Feature kRafAlignedInputEvents{"RafAlignedInput",
                                            base::FEATURE_DISABLED_BY_DEFAULT};