--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -1279,21 +1279,31 @@ pref("media.gmp.decoder.enabled", false)
 // installed.
 pref("media.gmp.decoder.aac", 2);
 pref("media.gmp.decoder.h264", 2);
 
 // Whether we should run a test-pattern through EME GMPs before assuming they'll
 // decode H.264.
 pref("media.gmp.trial-create.enabled", true);
 
+// Note: when media.gmp-*.visible is true, provided we're running on a
+// supported platform/OS version, the corresponding CDM appears in the
+// plugins list, Firefox will download the GMP/CDM if enabled, and our
+// UI to re-enable EME prompts the user to re-enable EME if it's disabled
+// and script requests EME. If *.visible is false, we won't show the UI
+// to enable the CDM if its disabled; it's as if the keysystem is completely
+// unsupported.
+
 #ifdef MOZ_ADOBE_EME
+pref("media.gmp-eme-adobe.visible", true);
 pref("media.gmp-eme-adobe.enabled", true);
 #endif
 
 #ifdef MOZ_WIDEVINE_EME
+pref("media.gmp-widevinecdm.visible", true);
 pref("media.gmp-widevinecdm.enabled", true);
 #endif
 
 // Play with different values of the decay time and get telemetry,
 // 0 means to randomize (and persist) the experiment value in users' profiles,
 // -1 means no experiment is run and we use the preferred value for frecency (6h)
 pref("browser.cache.frecency_experiment", 0);
 

--- a/toolkit/modules/GMPUtils.jsm
+++ b/toolkit/modules/GMPUtils.jsm
@@ -41,18 +41,18 @@ this.GMPUtils = {
    * @param   aPlugin
    *          The plugin to check.
    */
   isPluginHidden: function(aPlugin) {
     if (!aPlugin.isEME) {
       return false;
     }
 
-    if (!this._isPluginSupported(aPlugin) &&
-        !this._isPluginForcedVisible(aPlugin)) {
+    if (!this._isPluginSupported(aPlugin) ||
+        !this._isPluginVisible(aPlugin)) {
       this.maybeReportTelemetry(aPlugin.id,
                                 "VIDEO_EME_ADOBE_HIDDEN_REASON",
                                 GMPPluginHiddenReason.UNSUPPORTED);
       return true;
     }
 
     if (!GMPPrefs.get(GMPPrefs.KEY_EME_ENABLED, true)) {
       this.maybeReportTelemetry(aPlugin.id,
@@ -65,16 +65,19 @@ this.GMPUtils = {
   },
 
   /**
    * Checks whether or not a given plugin is supported by the current OS.
    * @param   aPlugin
    *          The plugin to check.
    */
   _isPluginSupported: function(aPlugin) {
+    if (this._isPluginForceSupported(aPlugin)) {
+      return true;
+    }
     if (aPlugin.id == EME_ADOBE_ID) {
       if (Services.appinfo.OS != "WINNT") {
         // Non-Windows OSes currently unsupported by Adobe EME
         this.maybeReportTelemetry(aPlugin.id,
                                   "VIDEO_EME_ADOBE_UNSUPPORTED_REASON",
                                   GMPPluginUnsupportedReason.NOT_WINDOWS);
         return false;
       }
@@ -87,23 +90,35 @@ this.GMPUtils = {
       }
       return false;
     }
 
     return true;
   },
 
   /**
-   * Checks whether or not a given plugin is forced visible. This can be used
-   * to test plugins that aren't yet supported by default on a particular OS.
+   * Checks whether or not a given plugin is visible in the addons manager
+   * UI and the "enable DRM" notification box. This can be used to test
+   * plugins that aren't yet turned on in the mozconfig.
    * @param   aPlugin
    *          The plugin to check.
    */
-  _isPluginForcedVisible: function(aPlugin) {
-    return GMPPrefs.get(GMPPrefs.KEY_PLUGIN_FORCEVISIBLE, false, aPlugin.id);
+  _isPluginVisible: function(aPlugin) {
+    return GMPPrefs.get(GMPPrefs.KEY_PLUGIN_VISIBLE, false, aPlugin.id);
+  },
+
+  /**
+   * Checks whether or not a given plugin is forced-supported. This is used
+   * in automated tests to override the checks that prevent GMPs running on an
+   * unsupported platform.
+   * @param   aPlugin
+   *          The plugin to check.
+   */
+  _isPluginForceSupported: function(aPlugin) {
+    return GMPPrefs.get(GMPPrefs.KEY_PLUGIN_FORCE_SUPPORTED, false, aPlugin.id);
   },
 
   /**
    * Report telemetry value, but only for Adobe CDM and only once per key
    * per session.
    */
   maybeReportTelemetry: function(aPluginId, key, value) {
     if (aPluginId != EME_ADOBE_ID) {
@@ -131,18 +146,19 @@ this.GMPUtils = {
  * Manages preferences for GMP addons
  */
 this.GMPPrefs = {
   KEY_EME_ENABLED:              "media.eme.enabled",
   KEY_PLUGIN_ENABLED:           "media.{0}.enabled",
   KEY_PLUGIN_LAST_UPDATE:       "media.{0}.lastUpdate",
   KEY_PLUGIN_VERSION:           "media.{0}.version",
   KEY_PLUGIN_AUTOUPDATE:        "media.{0}.autoupdate",
-  KEY_PLUGIN_FORCEVISIBLE:      "media.{0}.forcevisible",
+  KEY_PLUGIN_VISIBLE:           "media.{0}.visible",
   KEY_PLUGIN_ABI:               "media.{0}.abi",
+  KEY_PLUGIN_FORCE_SUPPORTED:   "media.{0}.forceSupported",
   KEY_URL:                      "media.gmp-manager.url",
   KEY_URL_OVERRIDE:             "media.gmp-manager.url.override",
   KEY_CERT_CHECKATTRS:          "media.gmp-manager.cert.checkAttributes",
   KEY_CERT_REQUIREBUILTIN:      "media.gmp-manager.cert.requireBuiltIn",
   KEY_UPDATE_LAST_CHECK:        "media.gmp-manager.lastCheck",
   KEY_SECONDS_BETWEEN_CHECKS:   "media.gmp-manager.secondsBetweenChecks",
   KEY_APP_DISTRIBUTION:         "distribution.id",
   KEY_APP_DISTRIBUTION_VERSION: "distribution.version",

--- a/toolkit/mozapps/extensions/test/browser/browser_gmpProvider.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_gmpProvider.js
@@ -97,17 +97,17 @@ add_task(function* initializeState() {
   registerCleanupFunction(Task.async(function*() {
     Services.obs.removeObserver(gOptionsObserver, AddonManager.OPTIONS_NOTIFICATION_DISPLAYED);
 
     for (let addon of gMockAddons) {
       gPrefs.clearUserPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_ENABLED, addon.id));
       gPrefs.clearUserPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_LAST_UPDATE, addon.id));
       gPrefs.clearUserPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_AUTOUPDATE, addon.id));
       gPrefs.clearUserPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_VERSION, addon.id));
-      gPrefs.clearUserPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_FORCEVISIBLE, addon.id));
+      gPrefs.clearUserPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_VISIBLE, addon.id));
     }
     gPrefs.clearUserPref(GMPScope.GMPPrefs.KEY_LOGGING_DUMP);
     gPrefs.clearUserPref(GMPScope.GMPPrefs.KEY_LOGGING_LEVEL);
     gPrefs.clearUserPref(GMPScope.GMPPrefs.KEY_UPDATE_LAST_CHECK);
     gPrefs.clearUserPref(GMPScope.GMPPrefs.KEY_EME_ENABLED);
     yield GMPScope.GMPProvider.shutdown();
     GMPScope.GMPProvider.startup();
   }));
@@ -120,17 +120,17 @@ add_task(function* initializeState() {
   // Start out with plugins not being installed, disabled and automatic updates
   // disabled.
   gPrefs.setBoolPref(GMPScope.GMPPrefs.KEY_EME_ENABLED, true);
   for (let addon of gMockAddons) {
     gPrefs.setBoolPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_ENABLED, addon.id), false);
     gPrefs.setIntPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_LAST_UPDATE, addon.id), 0);
     gPrefs.setBoolPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_AUTOUPDATE, addon.id), false);
     gPrefs.setCharPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_VERSION, addon.id), "");
-    gPrefs.setBoolPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_FORCEVISIBLE, addon.id),
+    gPrefs.setBoolPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_VISIBLE, addon.id),
                        true);
   }
   yield GMPScope.GMPProvider.shutdown();
   GMPScope.GMPProvider.startup();
 });
 
 add_task(function* testNotInstalledDisabled() {
   Assert.ok(gCategoryUtilities.isTypeVisible("plugin"), "Plugin tab visible.");
@@ -365,17 +365,17 @@ add_task(function* testUpdateButton() {
     writable: true,
     enumerable: true,
     configurable: true
   });
 });
 
 add_task(function* testEmeSupport() {
   for (let addon of gMockAddons) {
-    gPrefs.clearUserPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_FORCEVISIBLE, addon.id));
+    gPrefs.clearUserPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_VISIBLE, addon.id));
   }
   yield GMPScope.GMPProvider.shutdown();
   GMPScope.GMPProvider.startup();
 
   for (let addon of gMockAddons) {
     yield gCategoryUtilities.openType("plugin");
     let doc = gManagerWindow.document;
     let item = get_addon_element(gManagerWindow, addon.id);
@@ -395,17 +395,17 @@ add_task(function* testEmeSupport() {
                   "Widevine not supported, couldn't find add-on element.");
       }
     } else {
       Assert.ok(item, "Found add-on element.");
     }
   }
 
   for (let addon of gMockAddons) {
-    gPrefs.setBoolPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_FORCEVISIBLE, addon.id),
+    gPrefs.setBoolPref(getKey(GMPScope.GMPPrefs.KEY_PLUGIN_VISIBLE, addon.id),
                        true);
   }
   yield GMPScope.GMPProvider.shutdown();
   GMPScope.GMPProvider.startup();
 
 });
 
 add_task(function* test_cleanup() {

--- a/toolkit/mozapps/extensions/test/xpcshell/test_gmpProvider.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gmpProvider.js
@@ -54,17 +54,19 @@ MockGMPInstallManager.prototype = {
 function run_test() {
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "1.9.2");
   startupManager();
 
   gPrefs.setBoolPref(GMPScope.GMPPrefs.KEY_LOGGING_DUMP, true);
   gPrefs.setIntPref(GMPScope.GMPPrefs.KEY_LOGGING_LEVEL, 0);
   gPrefs.setBoolPref(GMPScope.GMPPrefs.KEY_EME_ENABLED, true);
   for (let addon of gMockAddons.values()) {
-    gPrefs.setBoolPref(gGetKey(GMPScope.GMPPrefs.KEY_PLUGIN_FORCEVISIBLE, addon.id),
+    gPrefs.setBoolPref(gGetKey(GMPScope.GMPPrefs.KEY_PLUGIN_VISIBLE, addon.id),
+                       true);
+    gPrefs.setBoolPref(gGetKey(GMPScope.GMPPrefs.KEY_PLUGIN_FORCE_SUPPORTED, addon.id),
                        true);
   }
   GMPScope.GMPProvider.shutdown();
   GMPScope.GMPProvider.startup();
 
   run_next_test();
 }