Changing IdentityManager::Observer and its subclasses to use CoreAccountId

This cl is part of the effort to use CoreAccountId instead of std::string
to denote account_id.

Bug: 959157
Change-Id: I0fd318d8034fb1294336f7534eb672fd1faeb084
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1611996
Reviewed-by: Mihai Sardarescu <[email protected]>
Reviewed-by: Sylvain Defresne <[email protected]>
Reviewed-by: Colin Blundell <[email protected]>
Commit-Queue: Tanmoy Mollik <[email protected]>
Cr-Commit-Position: refs/heads/master@{#661344}
diff --git a/components/invalidation/impl/profile_identity_provider.cc b/components/invalidation/impl/profile_identity_provider.cc
index 2bda764..ff26ade 100644
--- a/components/invalidation/impl/profile_identity_provider.cc
+++ b/components/invalidation/impl/profile_identity_provider.cc
@@ -116,7 +116,7 @@
 }
 
 void ProfileIdentityProvider::OnRefreshTokenRemovedForAccount(
-    const std::string& account_id) {
+    const CoreAccountId& account_id) {
   ProcessRefreshTokenRemovalForAccount(account_id);
 }