Bug 1732409 make getUserMedia() permission prompt requirement independent of "media.navigator.streams.fake" r=jib

"media.navigator.permission.disabled" exists for controlling the permission
prompt separately.

This will allow consolidation of camera and microphone preference handling
into EnumerateRawDevices().  Although auto-disabling permission with
"media.navigator.streams.fake" is sometimes useful for tests, it is actually
easier to consider them independently because sometimes the auto-disabling
needs to be overridden.

The logic to disable the permission prompt with content-exposed fake:true
parameter is maintained as is.

The CamerasParent usage of "media.navigator.permission.fake" seems to have
been a misunderstanding in
https://hg.mozilla.org/mozilla-central/rev/c5d6c3e00c91dd0595a12b145c66cf4f2a890591#l6.129

Differential Revision: https://phabricator.services.mozilla.com/D132897

dom/media/MediaManager.cpp

@@ -2685,14 +2685,15 @@ RefPtr<MediaManager::StreamPromise> MediaManager::GetUserMedia(
       audioEnumerationType = DeviceEnumerationType::Fake;
     }
   }
-
+  // fake:true is effective only for microphone and camera devices, so
-  bool realDevicesRequested =
+  // permission must be requested for screen capture even if fake:true is set.
-      (videoEnumerationType != DeviceEnumerationType::Fake && hasVideo) ||
+  bool hasOnlyForcedFakes =
-      (audioEnumerationType != DeviceEnumerationType::Fake && hasAudio);
+      forceFakes && (!hasVideo || videoType == MediaSourceEnum::Camera) &&
+      (!hasAudio || audioType == MediaSourceEnum::Microphone);
   bool askPermission =
       (!privileged ||
        Preferences::GetBool("media.navigator.permission.force")) &&
-      (realDevicesRequested ||
+      (!hasOnlyForcedFakes ||
        Preferences::GetBool("media.navigator.permission.fake"));
 
   LOG("%s: Preparing to enumerate devices. windowId=%" PRIu64

dom/media/autoplay/test/browser/browser_autoplay_policy_user_gestures.js

@@ -67,7 +67,6 @@ function setupTestPreferences() {
       ["media.autoplay.blocking_policy", 0],
       ["media.autoplay.block-event.enabled", true],
       ["media.autoplay.block-webaudio", true],
-      ["media.navigator.permission.fake", true],
     ],
   });
 }

dom/media/systemservices/CamerasParent.cpp

@@ -721,10 +721,9 @@ mozilla::ipc::IPCResult CamerasParent::RecvAllocateCapture(
         if (!allowed) {
           // Developer preference for turning off permission check.
           if (Preferences::GetBool("media.navigator.permission.disabled",
-                                   false) ||
+                                   false)) {
-              Preferences::GetBool("media.navigator.permission.fake")) {
             allowed = true;
-            LOG("No permission but checks are disabled or fake sources active");
+            LOG("No permission but checks are disabled");
           } else {
             LOG("No camera permission for this origin");
           }

dom/media/test/gUM_support.js

@@ -72,11 +72,8 @@ async function pushGetUserMediaTestPrefs({
       );
     }
   }
-  if (loopbackAudio || loopbackVideo) {
+  // Prevent presentation of the gUM permission prompt.
-    // Prevent gUM permission prompt. Since loopback devices are considered
+  testPrefs.push(["media.navigator.permission.disabled", true]);
-    // real devices we need to set prefs so the gUM prompt isn't presented.
-    testPrefs.push(["media.navigator.permission.disabled", true]);
-  }
   return SpecialPowers.pushPrefEnv({ set: testPrefs });
 }
 

dom/media/webrtc/tests/mochitests/test_getUserMedia_scarySources.html

@@ -28,7 +28,6 @@ let getDevices = async constraints => {
 
 runTest(async () => {
   await pushPrefs(["media.navigator.permission.disabled", true],
-                  ["media.navigator.permission.fake", true],
                   ["media.navigator.permission.force", true]);
   let devices = await getDevices({video: { mediaSource: "window" }});
   ok(devices.length, "Found one or more windows.");

testing/profiles/web-platform/user.js

@@ -21,6 +21,8 @@ user_pref("extensions.update.notifyUser", false);
 user_pref("focusmanager.testmode", true);
 // Enable fake media streams for getUserMedia
 user_pref("media.navigator.streams.fake", true);
+// Disable permission prompt for getUserMedia
+user_pref("media.navigator.permission.disabled", true);
 // Enable pre-fetching of resources
 user_pref("network.preload", true);
 // Enable direct connection