Implement an API to allow passing an "ap" parameter to component updates.

components/update_client/update_client.h

Index: components/update_client/update_client.h
diff --git a/components/update_client/update_client.h b/components/update_client/update_client.h
index e354fb6263996074393c8ad113ddd1df7f0a9a82..06f4f09da36897c917a086c7c1e4bb75022a3c82 100644
--- a/components/update_client/update_client.h
+++ b/components/update_client/update_client.h
@@ -196,6 +196,7 @@ struct CrxComponent {
 
   std::string fingerprint;  // Optional.
   std::string name;         // Optional.
+  std::string ap;           // Optional. Must match ^[-+_=a-zA-Z0-9]{0,256}$
 
   // Specifies that the CRX can be background-downloaded in some cases.
   // The default for this value is |true|.