Give ProtoDatabase access to Level DB's approximate memory usage.

This pipes the call to GetProperty from ProtoDatabase through to
leveldb_proto LevelDB and finally onto the underlying Level DB, so we
can retrieve the value for tests and metrics.

Bug: 870813
Change-Id: I23f89685017eeae77e19c37847d6399cc8d6085f
Reviewed-on: https://chromium-review.googlesource.com/1169878
Commit-Queue: Troy Hildebrandt <thildebr@chromium.org>
Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585252}

components/leveldb_proto/leveldb_database.cc

@@ -93,10 +93,8 @@ leveldb::Status LevelDB::Init(const base::FilePath& database_dir,
       // reads/writes and the block cache should be empty.
       uint64_t approx_mem = 0;
       std::string usage_string;
-      if (db_->GetProperty("leveldb.approximate-memory-usage", &usage_string) &&
-          base::StringToUint64(usage_string, &approx_mem)) {
+      if (GetApproximateMemoryUse(&approx_mem))
         approx_mem_histogram_->Add(approx_mem);
-      }
     }
   } else {
     LOG(WARNING) << "Unable to open " << database_dir.value() << ": "
@@ -236,4 +234,10 @@ bool LevelDB::Destroy() {
   return s.ok();
 }
 
+bool LevelDB::GetApproximateMemoryUse(uint64_t* approx_mem) {
+  std::string usage_string;
+  return (db_->GetProperty("leveldb.approximate-memory-usage", &usage_string) &&
+          base::StringToUint64(usage_string, approx_mem));
+}
+
 }  // namespace leveldb_proto

components/leveldb_proto/leveldb_database.h

@@ -64,6 +64,10 @@ class LevelDB {
   // directory.
   virtual bool Destroy();
 
+  // Returns true if we successfully read the approximate memory usage property
+  // from the LevelDB.
+  bool GetApproximateMemoryUse(uint64_t* approx_mem);
+
  private:
   FRIEND_TEST_ALL_PREFIXES(ProtoDatabaseImplLevelDBTest, TestDBInitFail);
 

components/leveldb_proto/proto_database_impl.h

@@ -70,6 +70,8 @@ class ProtoDatabaseImpl : public ProtoDatabase<T> {
                         const leveldb_env::Options& options,
                         typename ProtoDatabase<T>::InitCallback callback);
 
+  bool GetApproximateMemoryUse(uint64_t* approx_mem);
+
  private:
   base::ThreadChecker thread_checker_;
 
@@ -388,6 +390,11 @@ void ProtoDatabaseImpl<T>::GetEntry(
                      std::move(entry)));
 }
 
+template <typename T>
+bool ProtoDatabaseImpl<T>::GetApproximateMemoryUse(uint64_t* approx_mem) {
+  return db_->GetApproximateMemoryUse(approx_mem);
+}
+
 }  // namespace leveldb_proto
 
 #endif  // COMPONENTS_LEVELDB_PROTO_PROTO_DATABASE_IMPL_H_