Commander: empty string needle should not match anything

We do sometimes want to return results for an empty string, but that
decision should be made at a higher level than the fuzzy finder.

Bug: 1014639
Change-Id: I99c4a4ef37e9a58bd7154af0a37e66e675c188fa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2518209
Commit-Queue: Avi Drissman <avi@chromium.org>
Auto-Submit: Leonard Grey <lgrey@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#823777}

chrome/browser/ui/commander/fuzzy_finder.cc

@@ -141,6 +141,8 @@ namespace commander {
 double FuzzyFind(const base::string16& needle,
                  const base::string16& haystack,
                  std::vector<gfx::Range>* matched_ranges) {
+  if (needle.size() == 0)
+    return 0;
   DCHECK(needle == base::i18n::FoldCase(needle));
   matched_ranges->clear();
   const base::string16& folded = base::i18n::FoldCase(haystack);

chrome/browser/ui/commander/fuzzy_finder_unittest.cc

@@ -102,4 +102,12 @@ TEST(CommanderFuzzyFinder, Noncontiguous) {
   EXPECT_EQ(ranges,
             std::vector<gfx::Range>({{0, 1}, {6, 7}, {13, 14}, {19, 20}}));
 }
+
+TEST(CommanderFuzzyFinder, EmptyStringDoesNotMatch) {
+  std::vector<gfx::Range> ranges;
+  EXPECT_EQ(0, FuzzyFind(base::ASCIIToUTF16(""), base::ASCIIToUTF16("orange"),
+                         &ranges));
+  EXPECT_TRUE(ranges.empty());
+}
+
 }  // namespace commander