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..287f9f6894bd14ff7c6565afcfbb675cbea067a2 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: