Loading the account mappings from store to the driver.
This is to make sure the starting list of account
mapping properly reflects the mappings present in the
previous Chrome session.

BUG=374969

Review URL: https://codereview.chromium.org/600053002

Cr-Commit-Position: refs/heads/master@{#296567}
diff --git a/components/gcm_driver/gcm_client.h b/components/gcm_driver/gcm_client.h
index abf2fd5..740a3c7 100644
--- a/components/gcm_driver/gcm_client.h
+++ b/components/gcm_driver/gcm_client.h
@@ -201,7 +201,10 @@
     // Called when the GCM becomes ready. To get to this state, GCMClient
     // finished loading from the GCM store and retrieved the device check-in
     // from the server if it hadn't yet.
-    virtual void OnGCMReady() = 0;
+    // |account_mappings|: a persisted list of accounts mapped to this GCM
+    //                     client.
+    virtual void OnGCMReady(
+        const std::vector<AccountMapping>& account_mappings) = 0;
 
     // Called when activities are being recorded and a new activity has just
     // been recorded.