IndexedDB: Added UMA stat to measure time to close backing store.

Close can block on a background compaction, so log to reveal possible
performance issues.

BUG=502025

Review URL: https://codereview.chromium.org/1180803003

Cr-Commit-Position: refs/heads/master@{#335163}

2 files changed, 12 insertions, 1 deletions

diff --git a/content/browser/indexed_db/leveldb/leveldb_database.cc b/content/browser/indexed_db/leveldb/leveldb_database.cc
index 459a16e..2c18f1f 100644
--- a/content/browser/indexed_db/leveldb/leveldb_database.cc
+++ b/content/browser/indexed_db/leveldb/leveldb_database.cc
@@ -86,11 +86,20 @@ LevelDBDatabase::LevelDBDatabase() {}
 
 LevelDBDatabase::~LevelDBDatabase() {
   // db_'s destructor uses comparator_adapter_; order of deletion is important.
-  db_.reset();
+  CloseDatabase();
   comparator_adapter_.reset();
   env_.reset();
 }
 
+void LevelDBDatabase::CloseDatabase() {
+  if (db_) {
+    base::TimeTicks begin_time = base::TimeTicks::Now();
+    db_.reset();
+    UMA_HISTOGRAM_MEDIUM_TIMES("WebCore.IndexedDB.LevelDB.CloseTime",
+                               base::TimeTicks::Now() - begin_time);
+  }
+}
+
 static leveldb::Status OpenDB(
     leveldb::Comparator* comparator,
     leveldb::Env* env,
diff --git a/content/browser/indexed_db/leveldb/leveldb_database.h b/content/browser/indexed_db/leveldb/leveldb_database.h
index ddc6aa5..60a38ec 100644
--- a/content/browser/indexed_db/leveldb/leveldb_database.h
+++ b/content/browser/indexed_db/leveldb/leveldb_database.h
@@ -101,6 +101,8 @@ class CONTENT_EXPORT LevelDBDatabase {
  private:
   friend class LevelDBSnapshot;
 
+  void CloseDatabase();
+
   scoped_ptr<leveldb::Env> env_;
   scoped_ptr<leveldb::Comparator> comparator_adapter_;
   scoped_ptr<leveldb::DB> db_;