Purge browser cache for dom storage in a smarter way

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 26e984b0b2b19ebe9a15cd2190b5a5bad3b282be..6c1021c831e54cb7746cb81ed15d675590949188 100644
--- a/content/browser/dom_storage/dom_storage_area.cc
+++ b/content/browser/dom_storage/dom_storage_area.cc
@@ -303,6 +303,11 @@ void DOMStorageArea::DeleteOrigin() {
   }
 }
 
+void DOMStorageArea::TrimDatabase() {
+  if (backing_)

[michaeln, 2016/05/09 21:50:31]

There are some complications that i think make this problematic?

The db is used on two different 'sequences'. The initial import of data is
performed on the 'primary' sequence. Commits are the performed on the 'commit'
sequence. And the db can be reset on the 'primary' sequence when there are no
commits in flight.

A possible simplification to sidestep complexity stemming from that is to trim
the caches ever time we touch the db (see other comments in this file). 

Or consider leaving this part out for now.

[ssid, 2016/05/10 02:04:15]

Thanks, I didn't realize this issue.
Yes, post task might be overkill here and we are now clearing at commit, so i
removed this part.

+    backing_->TrimDatabase();
+}
+
 void DOMStorageArea::PurgeMemory() {
   DCHECK(!is_shutdown_);
   // Purging sessionStorage is not supported; it won't work with FastClear.