Remove kMediaDeviceIdSalt from incognito whitelist.

kMediaDeviceIdSalt is removed from incognito persistent preferences
list. After this CL, the changes to this preference in incognito mode
are not written to user profile.

Bug: 861722
Change-Id: If9328b582523573fb0f9cbcc7dbe89ff8b36c8b4
TBR: perkj@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/1255525
Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
Reviewed-by: Ramin Halavati <rhalavati@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595753}

chrome/browser/prefs/pref_service_incognito_whitelist.cc

@@ -209,7 +209,6 @@ const char* const kPersistentPrefNames[] = {
 // audited, checked with owners, and removed or transfered to
 // |kPersistentPrefNames|.
 const char* const kTemporaryIncognitoWhitelist[] = {
-    prefs::kMediaDeviceIdSalt,
     prefs::kClearPluginLSODataEnabled,
 };