Purge browser cache for dom storage in a smarter way

content/browser/dom_storage/dom_storage_area.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/dom_storage/dom_storage_area.h"
 
 #include <algorithm>
 #include <cctype>  // for std::isalnum
 
 #include "base/bind.h"
@@ skipping 353 matching lines @@
 
 void DOMStorageArea::InitialImportIfNeeded() {
   if (is_initial_import_done_)
     return;
 
   DCHECK(backing_.get());
 
   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;
   UMA_HISTOGRAM_TIMES("LocalStorage.BrowserTimeToPrimeLocalStorage",
                       time_to_import);
 
   size_t local_storage_size_kb = map_->bytes_used() / 1024;
   // Track localStorage size, from 0-6MB. Note that the maximum size should be
   // 5MB, but we add some slop since we want to make sure the max size is always
   // above what we see in practice, since histograms can't change.
@@ skipping 85 matching lines @@
                  base::Owned(commit_batch_.release())));
   ++commit_batches_in_flight_;
   DCHECK(success);
 }
 
 void DOMStorageArea::CommitChanges(const CommitBatch* commit_batch) {
   // This method executes on the commit sequence.
   DCHECK(task_runner_->IsRunningOnCommitSequence());
   backing_->CommitChanges(commit_batch->clear_all_first,
                           commit_batch->changed_values);
+  backing_->TrimMemory();

[michaeln, 2016/05/14 00:42:52]

What i meant by not exposing this in public api was that
DOMStorageDatabase::CommitChanges and ReadAllValues methods could internally
perform this function. So no public api or virtual adapter plumbing would be
needed.

[ssid, 2016/05/16 20:51:56]

Sorry, I was blind. Fixed this.

+
   // 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(
       FROM_HERE,
       base::Bind(&DOMStorageArea::OnCommitComplete, this));
 }
 
 void DOMStorageArea::OnCommitComplete() {
   // We're back on the primary sequence in this method.
   DCHECK(task_runner_->IsRunningOnPrimarySequence());
@@ skipping 18 matching lines @@
         commit_batch_->clear_all_first,
         commit_batch_->changed_values);
     DCHECK(success);
   }
   commit_batch_.reset();
   backing_.reset();
   session_storage_backing_ = NULL;
 }
 
 }  // namespace content