[Autofill/Autocomplete Feature] Substring matching instead of prefix matching.

components/autofill/core/common/autofill_util.h

Index: components/autofill/core/common/autofill_util.h
diff --git a/components/autofill/core/common/autofill_util.h b/components/autofill/core/common/autofill_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..cb770c3feffae3591b8c9fc09075dbd8642bb49a
--- /dev/null
+++ b/components/autofill/core/common/autofill_util.h
@@ -0,0 +1,32 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_AUTOFILL_CORE_COMMON_AUTOFILL_UTIL_H_
+#define COMPONENTS_AUTOFILL_CORE_COMMON_AUTOFILL_UTIL_H_
+
+#include "base/strings/string16.h"
+
+namespace autofill {
+
+// Returns |true| when command line switch
+// |kEnableSuggestionsWithSubstringMatch| is on; otherwise |false|.
+bool IsFeatureSubstringMatchEnabled();
+
+// Splits |field_suggestion| into tokens, separated by characters from " .,-_@".
+// Returns true if |field_content| is a prefix of some token; otherwise false.

[vabr (Chromium), 2015/03/30 14:51:03]

The comment seems different from what this function does.
Consider IsContentsPrefixOfSuggestionToken("a.b.c", "b.c", true).
According to the comment, this should return false, because "b.c" is not a
prefix of a token (the tokens are "a", "b", "c").

But the function actually returns true, if I understood it correctly, because it
is meant to start matching at the beginning of a token, and carry on across
token separators. That's why I was confused in the tests. Please check and
improve, if needed.

[Pritam Nikam, 2015/03/30 17:35:48]

Reverted back the logic aligned with the comments + added unit tests for the
same.

[vabr (Chromium), 2015/03/31 09:38:07]

Acknowledged.

+bool IsContentsPrefixOfSuggestionToken(const base::string16& field_suggestion,
+                                       const base::string16& field_contents,
+                                       bool case_sensitive);
+
+// Returns |field_contents|'s offset within the |field_suggestion| on successful
+// match and compute the selection range's |start| and |end| indices; otherwise
+// returns |base::string16::npos|.
+base::string16::size_type ComputeRange(const base::string16& field_suggestion,
+                                       const base::string16& field_contents,
+                                       size_t* start,
+                                       size_t* end);
+
+}  // namespace autofill
+
+#endif  // COMPONENTS_AUTOFILL_CORE_COMMON_AUTOFILL_UTIL_H_