Fix ParseCIDRBlock() to no longer accept invalid inputs.

net/base/ip_address_unittest.cc

Index: net/base/ip_address_unittest.cc
diff --git a/net/base/ip_address_unittest.cc b/net/base/ip_address_unittest.cc
index d78f6c342e97c3ab0bfd1b921e2b67febff55a73..3ebcb72a98c69b18b01333b76acaa0df6356ceec 100644
--- a/net/base/ip_address_unittest.cc
+++ b/net/base/ip_address_unittest.cc
@@ -252,7 +252,10 @@ TEST(IPAddressTest, ParseCIDRBlock_Invalid) {
                                       "::1/-3",
                                       "a::3/129",
                                       "::1/x",
-                                      "192.168.0.1//11"};
+                                      "192.168.0.1//11",
+                                      "192.168.1.1/+1",
+                                      "192.168.1.1/ +1",
+                                      "192.168.1.1/"};
 
   for (const auto& bad_literal : bad_literals) {
     IPAddress ip_address;