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

components/autofill/core/common/autofill_util.h

+// 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.
+bool IsFeatureSubstringMatchEnabled();
+
+// Returns true if the |field_contents| is a substring of the field's

[vabr (Chromium), 2015/07/13 14:04:26]

nit: What is "the field's |suggestion|"? Why not just "|suggestion|"?

[Pritam Nikam, 2015/07/14 10:30:07]

Done.

+// |suggestion| starting at token boundaries. |field_contents| can span multiple
+// |suggestion| tokens. A token is a sequences of contiguous characters
+// separated by any of the characters that are part of delimiter set {' ', '.',
+// ',', '-', '_', '@'}.
+bool FieldIsSuggestionSubstringStartingOnTokenBoundary(
+    const base::string16& suggestion,
+    const base::string16& field_contents,
+    bool case_sensitive);
+
+// Finds if the |field_contents| is a substring of the field's |suggestion|
+// starting at token boundaries. |field_contents| can span multiple |suggestion|
+// tokens. A token is a sequences of contiguous characters separated by any of

[vabr (Chromium), 2015/07/13 14:04:26]

Please do not repeat the definition of the token. This makes the comments bloat
and very hard to read, and the two copies will get out of sync eventually.
Instead, put a separate comment above line 16, explaining what is a token. Then
you can refer to it in both declaration comments. That will have multiple
benefits:
* no duplication
* all three comments will be simple, clear and easy to read
* definition of "token" will come before using it, which also increases
readability

[Pritam Nikam, 2015/07/14 10:30:07]

Done.

+// the characters that are part of delimiter set {' ', '.', ',', '-', '_', '@'}.
+// Returns the remaining autocompleted |suggestion| text's start position to
+// apply the text selection in the field; base::string16::npos otherwise.
+// "preview-on-hover" feature is one such use case where |field_contents| may
+// not match |suggestion|.
+size_t GetTextSelectionStart(const base::string16& suggestion,
+                             const base::string16& field_contents,
+                             bool case_sensitive);
+
+}  // namespace autofill
+
+#endif  // COMPONENTS_AUTOFILL_CORE_COMMON_AUTOFILL_UTIL_H_