Added a validator for JSON v3 schemas.

chrome/common/json_schema/json_schema_validator.h

Index: chrome/common/json_schema/json_schema_validator.h
diff --git a/chrome/common/json_schema/json_schema_validator.h b/chrome/common/json_schema/json_schema_validator.h
index e9a1a928a314b7dd2c7eaf216c91a7f4e760e0d6..3b42444c64296ee52ee3f148ee39cac1dc693423 100644
--- a/chrome/common/json_schema/json_schema_validator.h
+++ b/chrome/common/json_schema/json_schema_validator.h
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
 
 namespace base {
 class DictionaryValue;
@@ -98,6 +99,15 @@ class JSONSchemaValidator {
                                         const std::string& s1,
                                         const std::string& s2);
 
+  // Verifies if |schema| is a valid JSON v3 schema. When this validation passes
+  // then |schema| is valid JSON that can be parsed into a DictionaryValue,
+  // 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.
+  static scoped_ptr<base::DictionaryValue> IsValidSchema(
+      const std::string& schema,
+      std::string* error);

[not at google - send to devlin, 2013/05/16 17:08:20]

a static Create method which takes a std::string schema / error* and returns a
scoped_ptr<JSONSchemaValidator> would be easier to use. Transferring
dependencies (i.e. constructing a JSV depends on something that came from
IsValidSchema) is better factored that way.

However, it would probably require more invasive changes/restructuring to
json_schema_validator.cc. 

[Joao da Silva, 2013/05/19 13:16:29]

The returned DictionaryValue can be used to build a JSV, but for the
policy-for-extensions work it'll be used to build a PolicySchema instead. So I'd
leave the types signature as is, but I'm cool with moving this somewhere else or
renaming it, if you have better ideas.

+
   // Creates a validator for the specified schema.
   //
   // NOTE: This constructor assumes that |schema| is well formed and valid.