* Address file_size() in solana-labs#381. Remove TODO comments.

accounts-db/src/accounts_file.rs

@@ -113,15 +113,13 @@ impl AccountsFile {
     pub fn len(&self) -> usize {
         match self {
             Self::AppendVec(av) => av.len(),
-            // TODO(yhchiang): use cached result when the file is read-only
             Self::TieredStorage(ts) => ts.file_size().unwrap_or(0) as usize,
         }
     }
 
     pub fn is_empty(&self) -> bool {
         match self {
             Self::AppendVec(av) => av.is_empty(),
-            // TODO(yhchiang): use cached result when the file is read-only
             Self::TieredStorage(ts) => ts.file_size().unwrap_or(0) == 0,
         }
     }
@@ -132,7 +130,6 @@ impl AccountsFile {
             Self::TieredStorage(ts) => {
                 // As TieredStorage doesn't have the concept about capacity,
                 // here we return the file size when the file was written.
-                // TODO(yhchiang): use cached result when the file is read-only
                 if ts.is_read_only() {
                     return ts.file_size().unwrap_or(0);
                 }