Purge browser cache for dom storage in a smarter way

content/browser/dom_storage/dom_storage_database.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_database.h"
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "sql/statement.h"
@@ skipping 50 matching lines @@
                                                    "SELECT * from ItemTable"));
   DCHECK(statement.is_valid());
 
   while (statement.Step()) {
     base::string16 key = statement.ColumnString16(0);
     base::string16 value;
     statement.ColumnBlobAsString16(1, &value);
     (*result)[key] = base::NullableString16(value, false);
   }
   known_to_be_empty_ = result->empty();
+
+  // Reduce the size of sqlite caches.
+  db_->TrimMemory(false /* aggressively */);
 }
 
 bool DOMStorageDatabase::CommitChanges(bool clear_all_first,
                                        const DOMStorageValuesMap& changes) {
   if (!LazyOpen(!changes.empty())) {
     // If we're being asked to commit changes that will result in an
     // empty database, we return true if the database file doesn't exist.
     return clear_all_first && changes.empty() &&
            !base::PathExists(file_path_);
   }
@@ skipping 37 matching lines @@
   if (!known_to_be_empty_ && did_delete && !did_insert) {
     sql::Statement statement(db_->GetCachedStatement(SQL_FROM_HERE,
         "SELECT count(key) from ItemTable"));
     if (statement.Step())
       known_to_be_empty_ = statement.ColumnInt(0) == 0;
   }
 
   bool success = transaction.Commit();
   if (!success)
     known_to_be_empty_ = old_known_to_be_empty;
+
+  // Reduce the size of sqlite caches.
+  db_->TrimMemory(false /* aggressively */);
+
   return success;
 }
 
 bool DOMStorageDatabase::LazyOpen(bool create_if_needed) {
   if (failed_to_open_) {
     // Don't try to open a database that we know has failed
     // already.
     return false;
   }
 
@@ skipping 150 matching lines @@
       CreateTableV2() &&
       CommitChanges(false, values) &&
       migration.Commit();
 }
 
 void DOMStorageDatabase::Close() {
   db_.reset(NULL);
 }
 
 }  // namespace content