Bug 1386620 - dt-addon-prefs: move jsonview enabled pref outside of devtools addon;r=ochameau

DevTools preferences are loaded dynamically by calling DevtoolsPreferences.loadPrefs().
We can not preload them when the addon starts, otherwise this will slow down the startup
of Firefox.

But jsonview's converter-observer needs to check preferences to check if jsonview is
enabled very early. Moving devtools.jsonview.enabled to a separate preferences file
that is still processed by firefox fixes the issue.

The downside is that this pref will keep following m-c's release cycle and not the addon's.
But it is so generic it should not be a big issue.


MozReview-Commit-ID: HrD5IVe54Ks

--HG--
extra : rebase_source : bb85aa12ec92db7d11abdb002f0429123b173afd
extra : source : 9622410d90ad264933ee7d1147ed655615ac4a19

.eslintignore

@@ -138,8 +138,9 @@ devtools/shared/qrcode/tests/mochitest/test_decode.html
 devtools/shared/tests/mochitest/*.html
 devtools/shared/webconsole/test/test_*.html
 
-# Ignore devtools pre-processed files
+# Ignore devtools preferences files
 devtools/client/preferences/**
+devtools/shim/devtools-startup-prefs.js
 
 # Ignore devtools third-party libs
 devtools/shared/jsbeautify/*

browser/installer/package-manifest.in

@@ -635,6 +635,7 @@
 ; [DevTools Shim Files]
 @RESPATH@/browser/chrome/devtools-shim@JAREXT@
 @RESPATH@/browser/chrome/devtools-shim.manifest
+@RESPATH@/browser/@PREF_DIR@/devtools-startup-prefs.js
 
 ; DevTools
 @RESPATH@/browser/chrome/devtools@JAREXT@

devtools/client/preferences/devtools.js

@@ -353,8 +353,5 @@ pref("devtools.editor.autocomplete", true);
 // version for each user.
 pref("devtools.telemetry.tools.opened.version", "{}");
 
-// Enable the JSON View tool (an inspector for application/json documents).
-pref("devtools.jsonview.enabled", true);
-
 // Enable the HTML responsive design mode for all channels.
 pref("devtools.responsive.html.enabled", true);

devtools/shim/devtools-startup-prefs.js

@@ -0,0 +1,12 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This Devtools preferences file will be loaded as a usual Firefox preferences file.
+// Most DevTools prefs are included with the addon and loaded dynamically during the addon
+// startup. For preferences that are required before the addon is loaded or that we can't
+// process in JS, they can be defined in this file.
+// Note that this preference file follows Firefox release cycle.
+
+// Enable the JSON View tool (an inspector for application/json documents).
+pref("devtools.jsonview.enabled", true);

devtools/shim/moz.build

@@ -6,6 +6,10 @@
 
 JAR_MANIFESTS += ['jar.mn']
 
+JS_PREFERENCE_FILES += [
+    'devtools-startup-prefs.js',
+]
+
 # Register the about:debugging page only for 'addon' and 'all' builds.
 if CONFIG['MOZ_DEVTOOLS'] != 'server':
     EXTRA_COMPONENTS += [