Add install_source to CrxComponent.

This change would allow us to propagate extension install source to
the component updater protocol builder.

Bug: 
Change-Id: I8daa94f9a07c15b9301b1ca2a3f8cacdfd7fa894
Reviewed-on: https://chromium-review.googlesource.com/823289
Commit-Queue: Minh Nguyen <[email protected]>
Reviewed-by: Joshua Pawlicki <[email protected]>
Cr-Commit-Position: refs/heads/master@{#523930}
diff --git a/components/update_client/update_client.h b/components/update_client/update_client.h
index 10e9cd18e..a806057 100644
--- a/components/update_client/update_client.h
+++ b/components/update_client/update_client.h
@@ -253,6 +253,11 @@
 
   // Reasons why this component/extension is disabled.
   std::vector<int> disabled_reasons;
+
+  // Information about where the component/extension was installed from.
+  // For extension, this information is set from the update service, which
+  // gets the install source from the update URL.
+  std::string install_source;
 };
 
 // Called when a non-blocking call of UpdateClient completes.