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..2e47cb2e3300b08c12d5e030eb48222bc55d1b14 100644
--- a/content/browser/dom_storage/dom_storage_area.cc
+++ b/content/browser/dom_storage/dom_storage_area.cc
@@ -371,6 +371,7 @@ void DOMStorageArea::InitialImportIfNeeded() {
   base::TimeTicks before = base::TimeTicks::Now();
   DOMStorageValuesMap initial_values;
   backing_->ReadAllValues(&initial_values);
+  backing_->TrimMemory();
   map_->SwapValues(&initial_values);
   is_initial_import_done_ = true;
   base::TimeDelta time_to_import = base::TimeTicks::Now() - before;
@@ -476,6 +477,8 @@ void DOMStorageArea::CommitChanges(const CommitBatch* commit_batch) {
   DCHECK(task_runner_->IsRunningOnCommitSequence());
   backing_->CommitChanges(commit_batch->clear_all_first,
                           commit_batch->changed_values);
+  backing_->TrimMemory();
+
   // TODO(michaeln): what if CommitChanges returns false (e.g., we're trying to
   // commit to a DB which is in an inconsistent state?)
   task_runner_->PostTask(