Unify UUID/GUID generation code across base and blink

base/guid.h

Index: base/guid.h
diff --git a/base/guid.h b/base/guid.h
index c0a06f8858e3637aace7ebd03287e18b095e35e4..67267043f467a0ae00a3795eff71859949f3aad3 100644
--- a/base/guid.h
+++ b/base/guid.h
@@ -14,19 +14,25 @@
 
 namespace base {
 
-// Generate a 128-bit random GUID of the form: "%08X-%04X-%04X-%04X-%012llX".
+// Generate a 128-bit (pseudo) random GUID in the form of version 4 as described
+// in RFC 4122, section 4.4.
+// The format of GUID version 4 must be xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx,
+// where y is one of [8, 9, A, B].
+// The hexadecimal values "a" through "f" are output as lower case characters.
 // If GUID generation fails an empty string is returned.
-// The POSIX implementation uses pseudo random number generation to create
-// the GUID.  The Windows implementation uses system services.
 BASE_EXPORT std::string GenerateGUID();
 
 // Returns true if the input string conforms to the GUID format.
+// (Note that this does not strictly check version 4 format so that it accepts
+// GUID format that was generated by Windows system services.
+// IsValidVersion4GUID to perform stricter check.)
 BASE_EXPORT bool IsValidGUID(const std::string& guid);
 
-#if defined(OS_POSIX)
+// Returns true if the input string conforms to the version 4 GUID format.
+BASE_EXPORT bool IsValidVersion4GUID(const std::string& guid);
+
 // For unit testing purposes only.  Do not use outside of tests.
 BASE_EXPORT std::string RandomDataToGUIDString(const uint64_t bytes[2]);
-#endif
 
 }  // namespace base