Bug 1522930, delay GMP initialization until after first point to improve perceived performance. r=mconley

Differential Revision: https://phabricator.services.mozilla.com/D67165

--HG--
extra : moz-landing-system : lando

toolkit/mozapps/extensions/internal/GMPProvider.jsm

@@ -48,6 +48,8 @@ const NS_GRE_DIR = "GreD";
 const CLEARKEY_PLUGIN_ID = "gmp-clearkey";
 const CLEARKEY_VERSION = "0.1";
 
+const FIRST_CONTENT_PROCESS_TOPIC = "ipc:first-content-process-created";
+
 const GMP_LICENSE_INFO = "gmp_license_info";
 const GMP_PRIVACY_INFO = "gmp_privacy_info";
 const GMP_LEARN_MORE = "learn_more_label";
@@ -880,9 +882,10 @@ var GMPProvider = {
       }
     }
   },
-};
 
-AddonManagerPrivate.registerProvider(GMPProvider, [
+  observe(subject, topic, data) {
+    if (topic == FIRST_CONTENT_PROCESS_TOPIC) {
+      AddonManagerPrivate.registerProvider(GMPProvider, [
         new AddonManagerPrivate.AddonType(
           "plugin",
           URI_EXTENSION_STRINGS,
@@ -891,4 +894,14 @@ AddonManagerPrivate.registerProvider(GMPProvider, [
           6000,
           AddonManager.TYPE_SUPPORTS_ASK_TO_ACTIVATE
         ),
-]);
+      ]);
+      Services.obs.removeObserver(this, FIRST_CONTENT_PROCESS_TOPIC);
+    }
+  },
+
+  addObserver() {
+    Services.obs.addObserver(this, FIRST_CONTENT_PROCESS_TOPIC);
+  },
+};
+
+GMPProvider.addObserver();

toolkit/mozapps/extensions/test/xpcshell/test_gmpProvider.js

@@ -58,6 +58,11 @@ MockGMPInstallManager.prototype = {
 
 add_task(async function setup() {
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "1.9.2");
+
+  // The GMPProvider does not register until the first content process
+  // is launched, so we simulate that by firing this notification.
+  Services.obs.notifyObservers(null, "ipc:first-content-process-created");
+
   await promiseStartupManager();
 
   gPrefs.setBoolPref(GMPScope.GMPPrefs.KEY_LOGGING_DUMP, true);