Make extensions DSE persistent in browser prefs

chrome/browser/prefs/session_startup_pref.cc

Index: chrome/browser/prefs/session_startup_pref.cc
diff --git a/chrome/browser/prefs/session_startup_pref.cc b/chrome/browser/prefs/session_startup_pref.cc
index 7bcf8d03f0d69fdc2ecf524846bcb464e15ab352..345ce21c1b4935582c71fafc83968b858dd428fb 100644
--- a/chrome/browser/prefs/session_startup_pref.cc
+++ b/chrome/browser/prefs/session_startup_pref.cc
@@ -41,6 +41,11 @@ void URLListToPref(const base::ListValue* url_list, SessionStartupPref* pref) {
 
 }  // namespace
 
+const int SessionStartupPref::kPrefValueLast;
+const int SessionStartupPref::kPrefValueURLs;
+const int SessionStartupPref::kPrefValueNewTab;
+const int SessionStartupPref::kPrefValueMax;

[gab, 2016/12/06 19:35:04]

Why do you need this? They're in the public header already?

[vasilii, 2016/12/06 19:42:11]

The context is here
https://groups.google.com/a/chromium.org/forum/?utm_source=digest&utm_medium=...

[gab, 2016/12/06 19:51:44]

This thread is huge, any specific entry? The OP is about declaring constants
static (which is already the case in the header) so I still don't see why you
need to do this fwd-declaration here after the definition in the header.

[gab, 2016/12/07 16:26:27]

Ok I see [1] and in particular [2], but why wasn't this required before?

[1]
https://groups.google.com/a/chromium.org/d/msg/chromium-dev/pF7nAmUQ2uw/_hhBK...
[2] http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#454

[Alexander Yashkin, 2016/12/09 08:19:52]

I beleive vasilii answered this question below.

[gab, 2016/12/09 18:18:27]

Right he replied:
"""Before base::FundamentalValue() took an int parameter by value. Now the code
uses base::MakeUnique which does perfect forwarding and, therefore, captures the
reference to the constant. Probably, the workaround would be to use
WrapUnique."""

to which I replied:
"""feels like these constants should just be using an enum anyways (with
explicitly set values that is given relation with existing on-disk prefs), that
way they don't need extra storage, their names merely represents an inline
integral value."""

[Alexander Yashkin, 2016/12/11 16:34:32]

Ok, changed to enum.

+
 // static
 void SessionStartupPref::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {