Revert of Convert //net and //chromecast to std::unordered_*

chromecast/base/device_capabilities_impl.cc

Index: chromecast/base/device_capabilities_impl.cc
diff --git a/chromecast/base/device_capabilities_impl.cc b/chromecast/base/device_capabilities_impl.cc
index 60c2153ccf632ea56960a206b4b8316b837a6f5c..c3dfea0d07e590eb5e30957f536874a0e3fd1d0a 100644
--- a/chromecast/base/device_capabilities_impl.cc
+++ b/chromecast/base/device_capabilities_impl.cc
@@ -149,9 +149,11 @@
   DCHECK(validator);
 
   base::AutoLock auto_lock(validation_lock_);
+  bool added =
+      validator_map_.add(key, base::WrapUnique(new ValidatorInfo(validator)))
+          .second;
   // Check that a validator has not already been registered for this key
-  DCHECK_EQ(0u, validator_map_.count(key));
-  validator_map_[key] = base::WrapUnique(new ValidatorInfo(validator));
+  DCHECK(added);
 }
 
 void DeviceCapabilitiesImpl::Unregister(const std::string& key,