Bug 1490641 - Disable all Gecko specific UIs by default in release bu…

…ild r=m_kato

Currently, we have some Gecko specific editing UI:
- Resizers to resize <img>s, <table>s, absolutely positioned elements.
- Inline-table-editing UI to add/remove rows/columns.
- Grabber to move absolutely positioned element.

They are now disabled by default in Nightly and early-Beta. Starting from 64,
this patch makes them disabled by default even on release channel.

Note that the other browsers do not have those UIs and web apps can enable
them with document.execCommand() on Gecko anyway. Those UI usage is enough
low according to the telemetry, but a few users use them aggressively (see
bug 1452538 comment 19).

This is a request from W3C Editing API WG:
w3c/editing#171

Differential Revision: https://phabricator.services.mozilla.com/D6112

UltraBlame original commit: aeedb53775769e6ccc5bd361491529a71009b129

modules/libpref/init/all.js

@@ -9035,9 +9035,6 @@ misspellings
 500
 )
 ;
-#
-ifdef
-EARLY_BETA_OR_EARLIER
 pref
 (
 "
@@ -9074,46 +9071,6 @@ enabled_by_default
 false
 )
 ;
-#
-else
-pref
-(
-"
-editor
-.
-resizing
-.
-enabled_by_default
-"
-true
-)
-;
-pref
-(
-"
-editor
-.
-inline_table_editing
-.
-enabled_by_default
-"
-true
-)
-;
-pref
-(
-"
-editor
-.
-positioning
-.
-enabled_by_default
-"
-true
-)
-;
-#
-endif
 pref
 (
 "
@@ -19078,16 +19035,6 @@ srcdoc
 "
 )
 ;
-pref
-(
-"
-csp
-.
-overrule_content_privileged_about_uris_without_csp_whitelist
-"
-false
-)
-;
 #
 endif
 pref