Add regular expression support in json_schema component

components/json_schema/json_schema_validator.h

Index: components/json_schema/json_schema_validator.h
diff --git a/components/json_schema/json_schema_validator.h b/components/json_schema/json_schema_validator.h
index 4e8acaddfd983c68b10c02f126e29b6a498cc2ab..5a00f2d7d78c2fbffa29482e59d479901beeff67 100644
--- a/components/json_schema/json_schema_validator.h
+++ b/components/json_schema/json_schema_validator.h
@@ -32,7 +32,6 @@ class Value;
 // - disallow
 // - union types (but replaced with 'choices')
 // - number.maxDecimal
-// - string.pattern
 //
 // The following properties are not applicable to the interface exposed by
 // this class:
@@ -52,6 +51,8 @@ class Value;
 // - by default an "object" typed schema does not allow additional properties.
 //   if present, "additionalProperties" is to be a schema against which all
 //   additional properties will be validated.
+// - regular expression supports all syntaxes that re2 accepts.
+//   See https://code.google.com/p/re2/wiki/Syntax for details.
 //==============================================================================
 class JSONSchemaValidator {
  public:
@@ -110,6 +111,9 @@ class JSONSchemaValidator {
   // and that DictionaryValue can be used to build a JSONSchemaValidator.
   // Returns the parsed DictionaryValue when |schema| validated, otherwise
   // returns NULL. In that case, |error| contains an error description.
+  // For performance reason, currently IsValidSchema() won't check the
+  // correctness of regular expression used in "pattern" and "patternProperties"
+  // and in Validate() invalid regular expression don't accepts any strings.
   static scoped_ptr<base::DictionaryValue> IsValidSchema(
       const std::string& schema,
       std::string* error);