Add source column to chrome://policy showing the origins of policies.

components/policy/core/common/configuration_policy_provider.h

Index: components/policy/core/common/configuration_policy_provider.h
diff --git a/components/policy/core/common/configuration_policy_provider.h b/components/policy/core/common/configuration_policy_provider.h
index e91ac21e3977e21a3347dda723dfe7f3ed532834..7d59e6f5831669026089d4a31d8132c78c6b6b7d 100644
--- a/components/policy/core/common/configuration_policy_provider.h
+++ b/components/policy/core/common/configuration_policy_provider.h
@@ -74,6 +74,8 @@ class POLICY_EXPORT ConfigurationPolicyProvider
   void OnSchemaRegistryUpdated(bool has_new_schemas) override;
   void OnSchemaRegistryReady() override;
 
+  PolicySource source() const { return source_; }
+
  protected:
   // Subclasses must invoke this to update the policies currently served by
   // this provider. UpdatePolicy() takes ownership of |policies|.
@@ -84,7 +86,14 @@ class POLICY_EXPORT ConfigurationPolicyProvider
 
   const scoped_refptr<SchemaMap>& schema_map() const;
 
+  // This provider provides policies only from one source at a time (defaulting
+  // to POLICY_SOURCE_UNKNOWN).
+  PolicySource source_;
+
  private:
+  // Used to tag all policies provided as coming from |source_|.
+  void SetPolicySources();
+
   // The policies currently configured at this provider.
   PolicyBundle policy_bundle_;