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

components/autofill/core/browser/webdata/autofill_table.cc

Index: components/autofill/core/browser/webdata/autofill_table.cc
diff --git a/components/autofill/core/browser/webdata/autofill_table.cc b/components/autofill/core/browser/webdata/autofill_table.cc
index c337f60223f165cecc20a75e0ae7808ddaf7f800..b3f352b0119b12f0047f5d030124f5cdc15f4bf7 100644
--- a/components/autofill/core/browser/webdata/autofill_table.cc
+++ b/components/autofill/core/browser/webdata/autofill_table.cc
@@ -18,6 +18,7 @@
 #include "base/logging.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
 #include "components/autofill/core/browser/autofill_country.h"
@@ -28,6 +29,7 @@
 #include "components/autofill/core/browser/webdata/autofill_change.h"
 #include "components/autofill/core/browser/webdata/autofill_entry.h"
 #include "components/autofill/core/common/autofill_switches.h"
+#include "components/autofill/core/common/autofill_util.h"
 #include "components/autofill/core/common/form_field_data.h"
 #include "components/os_crypt/os_crypt.h"
 #include "components/webdata/common/web_database.h"
@@ -368,6 +370,20 @@ CreditCard::ServerStatus ServerStatusStringToEnum(const std::string& status) {
   return CreditCard::OK;
 }
 
+// Returns string with sustituted (_), (%) and (!) in supplied |str| by (!_),
+// (!%) and (!!) respectively.
+// For e.g. "ex!a_mp%le" -> "ex!!a!_mp!%le".
+base::string16 SubstringSubstituteText(const base::string16& str) {
+  base::string16 result;
+  base::ReplaceChars(str, base::ASCIIToUTF16("!"), base::ASCIIToUTF16("!!"),
+                     &result);
+  base::ReplaceChars(result, base::ASCIIToUTF16("_"), base::ASCIIToUTF16("!_"),
+                     &result);
+  base::ReplaceChars(result, base::ASCIIToUTF16("%"), base::ASCIIToUTF16("!%"),
+                     &result);
+  return result;
+}
+
 }  // namespace
 
 // The maximum length allowed for form data.
@@ -456,9 +472,10 @@ bool AutofillTable::GetFormValuesForElementName(
     std::vector<base::string16>* values,
     int limit) {
   DCHECK(values);
-  sql::Statement s;
+  bool succeeded = false;
 
   if (prefix.empty()) {
+    sql::Statement s;
     s.Assign(db_->GetUniqueStatement(
         "SELECT value FROM autofill "
         "WHERE name = ? "
@@ -466,28 +483,74 @@ bool AutofillTable::GetFormValuesForElementName(
         "LIMIT ?"));
     s.BindString16(0, name);
     s.BindInt(1, limit);
+
+    values->clear();
+    while (s.Step())
+      values->push_back(s.ColumnString16(0));
+
+    succeeded = s.Succeeded();
   } else {
     base::string16 prefix_lower = base::i18n::ToLower(prefix);
     base::string16 next_prefix = prefix_lower;
     next_prefix[next_prefix.length() - 1]++;
 
-    s.Assign(db_->GetUniqueStatement(
+    sql::Statement s1;
+    s1.Assign(db_->GetUniqueStatement(
         "SELECT value FROM autofill "
         "WHERE name = ? AND "
         "value_lower >= ? AND "
         "value_lower < ? "
         "ORDER BY count DESC "
         "LIMIT ?"));
-    s.BindString16(0, name);
-    s.BindString16(1, prefix_lower);
-    s.BindString16(2, next_prefix);
-    s.BindInt(3, limit);
+    s1.BindString16(0, name);
+    s1.BindString16(1, prefix_lower);
+    s1.BindString16(2, next_prefix);
+    s1.BindInt(3, limit);
+
+    values->clear();
+    while (s1.Step())
+      values->push_back(s1.ColumnString16(0));
+
+    succeeded = s1.Succeeded();
+
+    if (IsFeatureSubstringMatchEnabled()) {
+      base::string16 substituted_text = SubstringSubstituteText(prefix_lower);
+      sql::Statement s2;
+      s2.Assign(db_->GetUniqueStatement(
+          "SELECT value FROM autofill "
+          "WHERE name = ? AND ("
+          " value LIKE ? ESCAPE '!' OR "
+          " value LIKE ? ESCAPE '!' OR "
+          " value LIKE ? ESCAPE '!' OR "
+          " value LIKE ? ESCAPE '!' OR "
+          " value LIKE ? ESCAPE '!' OR "
+          " value LIKE ? ESCAPE '!') "
+          "ORDER BY count DESC "
+          "LIMIT ?"));
+      s2.BindString16(0, name);
+      s2.BindString16(1, base::ASCIIToUTF16("% ") + substituted_text +
+                             base::ASCIIToUTF16("%"));
+      s2.BindString16(2, base::ASCIIToUTF16("%.") + substituted_text +
+                             base::ASCIIToUTF16("%"));
+      s2.BindString16(3, base::ASCIIToUTF16("%,") + substituted_text +
+                             base::ASCIIToUTF16("%"));
+      s2.BindString16(4, base::ASCIIToUTF16("%-") + substituted_text +
+                             base::ASCIIToUTF16("%"));
+      s2.BindString16(5, base::ASCIIToUTF16("%@") + substituted_text +
+                             base::ASCIIToUTF16("%"));
+      s2.BindString16(6, base::ASCIIToUTF16("%!_") + substituted_text +
+                             base::ASCIIToUTF16("%"));
+      s2.BindInt(7, limit);
+
+      // Append substring matched suggestions.
+      while (s2.Step())
+        values->push_back(s2.ColumnString16(0));
+
+      succeeded |= s2.Succeeded();
+    }
   }
 
-  values->clear();
-  while (s.Step())
-    values->push_back(s.ColumnString16(0));
-  return s.Succeeded();
+  return succeeded;
 }
 
 bool AutofillTable::HasFormElements() {