Bug 1630228 - Basic implementation to disable F12 until toolbox opens r=nchevobbe

In this changeset, we add a preference that will simply disable F12 when it is set.
UI and tests are in followup patches

Differential Revision: https://phabricator.services.mozilla.com/D71035

devtools/client/framework/devtools-browser.js

@@ -70,6 +70,10 @@ const L10N = new LocalizationHelper(
 
 const BROWSER_STYLESHEET_URL = "chrome://devtools/skin/devtools-browser.css";
 
+// XXX: This could also be moved to DevToolsStartup, which is the first
+// "entry point" for DevTools shortcuts and forwards the events
+// devtools-browser.
+const DEVTOOLS_F12_DISABLED_PREF = "devtools.experiment.f12.shortcut_disabled";
 /**
  * gDevToolsBrowser exposes functions to connect the gDevTools instance with a
  * Firefox instance.
@@ -299,9 +303,24 @@ var gDevToolsBrowser = (exports.gDevToolsBrowser = {
     // Otherwise implement all other key shortcuts individually here
     switch (key.id) {
       case "toggleToolbox":
-      case "toggleToolboxF12":
         await gDevToolsBrowser.toggleToolboxCommand(window.gBrowser, startTime);
         break;
+      case "toggleToolboxF12":
+        // See Bug 1630228. F12 is responsible for most of the accidental usage
+        // of DevTools. The preference here is used as part of an experiment to
+        // disable the F12 shortcut by default.
+        const isF12Disabled = Services.prefs.getBoolPref(
+          DEVTOOLS_F12_DISABLED_PREF,
+          false
+        );
+
+        if (!isF12Disabled) {
+          await gDevToolsBrowser.toggleToolboxCommand(
+            window.gBrowser,
+            startTime
+          );
+        }
+        break;
       case "browserToolbox":
         BrowserToolboxLauncher.init();
         break;

devtools/client/framework/toolbox.js

@@ -212,6 +212,8 @@ loader.lazyRequireGetter(
   "devtools/shared/picker-constants"
 );
 
+const DEVTOOLS_F12_DISABLED_PREF = "devtools.experiment.f12.shortcut_disabled";
+
 /**
  * A "Toolbox" is the component that holds all the tools for one specific
  * target. Visually, it's a document that includes the tools tabs and all
@@ -253,6 +255,12 @@ function Toolbox(
   // must use the time since the system wide epoch as the session ID.
   this.sessionId = msSinceProcessStart;
 
+  // If the user opened the toolbox, we can now enable the F12 shortcut.
+  if (Services.prefs.getBoolPref(DEVTOOLS_F12_DISABLED_PREF, false)) {
+    // Flip the preference.
+    Services.prefs.setBoolPref(DEVTOOLS_F12_DISABLED_PREF, false);
+  }
+
   // Map of the available DevTools WebExtensions:
   //   Map<extensionUUID, extensionName>
   this._webExtensions = new Map();

modules/libpref/init/all.js

@@ -4911,6 +4911,9 @@ pref("devtools.devices.url", "https://code.cdn.mozilla.net/devices/devices.json"
 // Enable Inactive CSS detection; used both by the client and the server.
 pref("devtools.inspector.inactive.css.enabled", true);
 
+// The F12 experiment aims at disabling f12 on selected profiles.
+pref("devtools.experiment.f12.shortcut_disabled", false);
+
 #if defined(NIGHTLY_BUILD) || defined(MOZ_DEV_EDITION)
 // Define in StaticPrefList.yaml and override here since StaticPrefList.yaml
 // doesn't provide a way to lock the pref