Foreign tab suggestions should update when disabling sync or signing out.

components/sync_sessions/open_tabs_ui_delegate.h

Index: components/sync_sessions/open_tabs_ui_delegate.h
diff --git a/components/sync_sessions/open_tabs_ui_delegate.h b/components/sync_sessions/open_tabs_ui_delegate.h
index cf8fd5faee4d2ee2b5c97fb7ef16f2d9676a1dc3..66b11d4173639aedb44556d1191af5e6fd54aafb 100644
--- a/components/sync_sessions/open_tabs_ui_delegate.h
+++ b/components/sync_sessions/open_tabs_ui_delegate.h
@@ -34,7 +34,7 @@ class OpenTabsUIDelegate {
   // session |tag|. Caller does NOT own the SessionTab object.
   // Returns true if the foreign session and tab were found, false otherwise.
   virtual bool GetForeignTab(const std::string& tag,
-                             const SessionID::id_type tab_id,

[maxbogue, 2016/12/16 22:21:34]

Why's this const being removed? Is this left over from another patch or is it
necessary for the mock?

[skym, 2016/12/19 20:31:43]

Necessary for the mock. So my theory, is that someone (maybe GMOCK) was dropping
the const on the primitive (SessionID::id_type), because it doesn't do anything
on a pure virtual method. However, not everyone dropped it, and MSVC always
complained about the mismatch. I tried dropping just the const from my gmock
usage (see PS#3) but that didn't help.

So, instead, I dropped the const from everything (except for
sessions_sync_manager.cc), and compilation was happy. I didn't think it warrants
a comment because

1) const on primitives on virtual methods is pointless
2) if you try to change this, you'll get a compile error

+                             SessionID::id_type tab_id,
                              const sessions::SessionTab** tab) = 0;
 
   // Delete a foreign session and all its sync data.