Add UMA metrics for desktop memory pressure notifications.

content/browser/dom_storage/dom_storage_area.cc

Index: content/browser/dom_storage/dom_storage_area.cc
diff --git a/content/browser/dom_storage/dom_storage_area.cc b/content/browser/dom_storage/dom_storage_area.cc
index 69c90596b0767a9b23baa5a6ff0930830c202257..94e376dc157db33287af156568cfd4d0df624118 100644
--- a/content/browser/dom_storage/dom_storage_area.cc
+++ b/content/browser/dom_storage/dom_storage_area.cc
@@ -307,6 +307,7 @@ void DOMStorageArea::DeleteOrigin() {
 }
 
 void DOMStorageArea::PurgeMemory() {
+/*
   DCHECK(!is_shutdown_);
   // Purging sessionStorage is not supported; it won't work with FastClear.
   DCHECK(!session_storage_backing_.get());
@@ -323,6 +324,7 @@ void DOMStorageArea::PurgeMemory() {
   // Recreate the database object, this frees up the open sqlite connection
   // and its page cache.
   backing_->Reset();
+  */
 }
 
 void DOMStorageArea::Shutdown() {