Tiny optimization in auto completion of Drive files.

This patch filters out candidates based on the timestamp,
before testing filename match or accessing resource metadata
DB for file path resolution.

BUG=none
TEST=With debug build and with a large account, type "a" in the search box
of Files.app. It should become faster.

Review URL: https://chromiumcodereview.appspot.com/15757009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202404 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/chromeos/drive/search_metadata.cc

@@ -127,6 +127,13 @@ void MaybeAddEntryToResult(
     const ResourceEntry& entry) {
   DCHECK_GE(at_most_num_matches, result_candidates->size());
 
+  // If the candidate set is already full, and this |entry| is old, do nothing.
+  // We perform this check first in order to avoid the costly find-and-highlight
+  // or FilePath lookup as much as possible.
+  if (result_candidates->size() == at_most_num_matches &&
+      !CompareByTimestamp(entry, result_candidates->top()->entry))
+    return;
+
   // Add |entry| to the result if the entry is eligible for the given
   // |options| and matches the query. The base name of the entry must
   // contains |query| to match the query.
@@ -140,13 +147,9 @@ void MaybeAddEntryToResult(
     return;
 
   // Make space for |entry| when appropriate.
-  if (result_candidates->size() == at_most_num_matches &&
-      CompareByTimestamp(entry, result_candidates->top()->entry))
+  if (result_candidates->size() == at_most_num_matches)
     result_candidates->pop();
-
-  // Add |entry| to the result when appropriate.
-  if (result_candidates->size() < at_most_num_matches)
-    result_candidates->push(new MetadataSearchResult(path, entry, highlighted));
+  result_candidates->push(new MetadataSearchResult(path, entry, highlighted));
 }
 
 // Implements SearchMetadata().