Use std::unique_ptr to express ownership of base::Value in PolicyMap::Entry

components/policy/core/common/policy_loader_win.cc

Index: components/policy/core/common/policy_loader_win.cc
diff --git a/components/policy/core/common/policy_loader_win.cc b/components/policy/core/common/policy_loader_win.cc
index d739a038a030658d6779f0d55432bde312925cf1..4981cf4d18d43e6a1a4cce79571413dcc6238dca 100644
--- a/components/policy/core/common/policy_loader_win.cc
+++ b/components/policy/core/common/policy_loader_win.cc
@@ -166,9 +166,11 @@ void FilterUntrustedPolicy(PolicyMap* policy) {
       filtered_values->AppendString(entry);
     }
     if (invalid_policies) {
-      policy->Set(key::kExtensionInstallForcelist,
-                  map_entry->level, map_entry->scope, map_entry->source,
-                  filtered_values.release(),
+      policy->Set(key::kExtensionInstallForcelist, map_entry->level,
+                  map_entry->scope, map_entry->source,
+                  std::move(filtered_values),
+                  // TODO(dcheng): Ummm... figure out what this is all about
+                  // when I'm more awake.

[Andrew T Wilson (Slow), 2016/05/03 11:59:03]

What's the concern here?

[dcheng, 2016/05/03 23:40:40]

ExternalDataFetcher is now an owned pointer, so it can't just be passed around
like this. Ordinarily, I would just transfer ownership, but that's not possible
here: PolicyMap::Get() returns a const Entry*.

Instead, I opted to just use Entry::DeepCopy() to build a new entry with the
correct filtered values. From a pure efficiency standpoint, it's probably a bit
suboptimal (since it clones the original Value and then immediately replaces it
with the filtered one), but I figure this code shouldn't be on the hot path
anyway, so the cost shouldn't be too large.

                   map_entry->external_data_fetcher);
 
       const PolicyDetails* details = GetChromePolicyDetails(