--- a/browser/base/content/content.js
+++ b/browser/base/content/content.js
@@ -8,17 +8,16 @@
 
 /* eslint-env mozilla/frame-script */
 
 var {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource:///modules/ContentWebRTC.jsm");
-Cu.import("resource:///modules/ContentObservers.jsm");
 Cu.import("resource://gre/modules/InlineSpellChecker.jsm");
 Cu.import("resource://gre/modules/InlineSpellCheckerContent.jsm");
 Cu.import("resource://gre/modules/Task.jsm");
 
 XPCOMUtils.defineLazyModuleGetter(this, "E10SUtils",
   "resource:///modules/E10SUtils.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "BrowserUtils",
   "resource://gre/modules/BrowserUtils.jsm");

rename from browser/modules/ContentObservers.jsm
rename to browser/modules/ContentObservers.js

--- a/browser/modules/moz.build
+++ b/browser/modules/moz.build
@@ -15,17 +15,17 @@ EXTRA_JS_MODULES += [
     'AboutNewTab.jsm',
     'AttributionCode.jsm',
     'BrowserUITelemetry.jsm',
     'BrowserUsageTelemetry.jsm',
     'CastingApps.jsm',
     'ContentClick.jsm',
     'ContentCrashHandlers.jsm',
     'ContentLinkHandler.jsm',
-    'ContentObservers.jsm',
+    'ContentObservers.js',
     'ContentSearch.jsm',
     'ContentWebRTC.jsm',
     'DirectoryLinksProvider.jsm',
     'E10SUtils.jsm',
     'ExtensionsUI.jsm',
     'Feeds.jsm',
     'FormSubmitObserver.jsm',
     'FormValidationHandler.jsm',

--- a/toolkit/components/processsingleton/MainProcessSingleton.js
+++ b/toolkit/components/processsingleton/MainProcessSingleton.js
@@ -70,16 +70,17 @@ MainProcessSingleton.prototype = {
       Services.obs.addObserver(this, "xpcom-shutdown", false);
 
       // Load this script early so that console.* is initialized
       // before other frame scripts.
       Services.mm.loadFrameScript("chrome://global/content/browser-content.js", true);
       Services.ppmm.loadProcessScript("chrome://global/content/process-content.js", true);
       Services.ppmm.addMessageListener("Console:Log", this.logConsoleMessage);
       Services.mm.addMessageListener("Search:AddEngine", this.addSearchEngine);
+      Services.ppmm.loadProcessScript("resource:///modules/ContentObservers.js", true);
       break;
     }
 
     case "xpcom-shutdown":
       Services.ppmm.removeMessageListener("Console:Log", this.logConsoleMessage);
       Services.mm.removeMessageListener("Search:AddEngine", this.addSearchEngine);
       break;
     }

--- a/tools/lint/eslint/modules.json
+++ b/tools/lint/eslint/modules.json
@@ -40,17 +40,17 @@
   "collection_validator.js": ["CollectionValidator", "CollectionProblemData"],
   "Console.jsm": ["console", "ConsoleAPI"],
   "constants.js": ["WEAVE_VERSION", "SYNC_API_VERSION", "USER_API_VERSION", "MISC_API_VERSION", "STORAGE_VERSION", "PREFS_BRANCH", "PWDMGR_HOST", "PWDMGR_PASSWORD_REALM", "PWDMGR_PASSPHRASE_REALM", "PWDMGR_KEYBUNDLE_REALM", "DEFAULT_KEYBUNDLE_NAME", "HMAC_INPUT", "SYNC_KEY_ENCODED_LENGTH", "SYNC_KEY_DECODED_LENGTH", "SYNC_KEY_HYPHENATED_LENGTH", "NO_SYNC_NODE_INTERVAL", "MAX_ERROR_COUNT_BEFORE_BACKOFF", "MAX_IGNORE_ERROR_COUNT", "MINIMUM_BACKOFF_INTERVAL", "MAXIMUM_BACKOFF_INTERVAL", "HMAC_EVENT_INTERVAL", "MASTER_PASSWORD_LOCKED_RETRY_INTERVAL", "DEFAULT_BLOCK_PERIOD", "MOBILE_BATCH_SIZE", "DEFAULT_GUID_FETCH_BATCH_SIZE", "DEFAULT_MOBILE_GUID_FETCH_BATCH_SIZE", "DEFAULT_STORE_BATCH_SIZE", "HISTORY_STORE_BATCH_SIZE", "FORMS_STORE_BATCH_SIZE", "PASSWORDS_STORE_BATCH_SIZE", "ADDONS_STORE_BATCH_SIZE", "APPS_STORE_BATCH_SIZE", "DEFAULT_DOWNLOAD_BATCH_SIZE", "SINGLE_USER_THRESHOLD", "MULTI_DEVICE_THRESHOLD", "SCORE_INCREMENT_SMALL", "SCORE_INCREMENT_MEDIUM", "SCORE_INCREMENT_XLARGE", "SCORE_UPDATE_DELAY", "IDLE_OBSERVER_BACK_DELAY", "MAX_UPLOAD_RECORDS", "MAX_UPLOAD_BYTES", "MAX_HISTORY_UPLOAD", "MAX_HISTORY_DOWNLOAD", "NOTIFY_TAB_SENT_TTL_SECS", "STATUS_OK", "SYNC_FAILED", "LOGIN_FAILED", "SYNC_FAILED_PARTIAL", "CLIENT_NOT_CONFIGURED", "STATUS_DISABLED", "MASTER_PASSWORD_LOCKED", "LOGIN_SUCCEEDED", "SYNC_SUCCEEDED", "ENGINE_SUCCEEDED", "LOGIN_FAILED_NO_USERNAME", "LOGIN_FAILED_NO_PASSWORD", "LOGIN_FAILED_NO_PASSPHRASE", "LOGIN_FAILED_NETWORK_ERROR", "LOGIN_FAILED_SERVER_ERROR", "LOGIN_FAILED_INVALID_PASSPHRASE", "LOGIN_FAILED_LOGIN_REJECTED", "METARECORD_DOWNLOAD_FAIL", "VERSION_OUT_OF_DATE", "DESKTOP_VERSION_OUT_OF_DATE", "SETUP_FAILED_NO_PASSPHRASE", "CREDENTIALS_CHANGED", "ABORT_SYNC_COMMAND", "NO_SYNC_NODE_FOUND", "OVER_QUOTA", "PROLONGED_SYNC_FAILURE", "SERVER_MAINTENANCE", "RESPONSE_OVER_QUOTA", "ENGINE_UPLOAD_FAIL", "ENGINE_DOWNLOAD_FAIL", "ENGINE_UNKNOWN_FAIL", "ENGINE_APPLY_FAIL", "ENGINE_METARECORD_DOWNLOAD_FAIL", "ENGINE_METARECORD_UPLOAD_FAIL", "ENGINE_BATCH_INTERRUPTED", "JPAKE_ERROR_CHANNEL", "JPAKE_ERROR_NETWORK", "JPAKE_ERROR_SERVER", "JPAKE_ERROR_TIMEOUT", "JPAKE_ERROR_INTERNAL", "JPAKE_ERROR_INVALID", "JPAKE_ERROR_NODATA", "JPAKE_ERROR_KEYMISMATCH", "JPAKE_ERROR_WRONGMESSAGE", "JPAKE_ERROR_USERABORT", "JPAKE_ERROR_DELAYUNSUPPORTED", "INFO_COLLECTIONS", "INFO_COLLECTION_USAGE", "INFO_COLLECTION_COUNTS", "INFO_QUOTA", "kSyncMasterPasswordLocked", "kSyncWeaveDisabled", "kSyncNetworkOffline", "kSyncBackoffNotMet", "kFirstSyncChoiceNotMade", "FIREFOX_ID", "FENNEC_ID", "SEAMONKEY_ID", "TEST_HARNESS_ID", "MIN_PP_LENGTH", "MIN_PASS_LENGTH", "DEVICE_TYPE_DESKTOP", "DEVICE_TYPE_MOBILE", "SQLITE_MAX_VARIABLE_NUMBER"],
   "Constants.jsm": ["Roles", "Events", "Relations", "Filters", "States", "Prefilters"],
   "ContactDB.jsm": ["ContactDB", "DB_NAME", "STORE_NAME", "SAVED_GETALL_STORE_NAME", "REVISION_STORE", "DB_VERSION"],
   "content-server.jsm": ["init"],
   "content.jsm": ["registerContentFrame"],
   "ContentCrashHandlers.jsm": ["TabCrashHandler", "PluginCrashReporter", "UnsubmittedCrashHandler"],
-  "ContentObservers.jsm": [],
+  "ContentObservers.js": [],
   "ContentPrefUtils.jsm": ["ContentPref", "cbHandleResult", "cbHandleError", "cbHandleCompletion", "safeCallback", "_methodsCallableFromChild"],
   "controller.js": ["MozMillController", "globalEventRegistry", "sleep", "windowMap"],
   "cookies.js": ["Cookies"],
   "CoverageUtils.jsm": ["CoverageCollector"],
   "CrashManagerTest.jsm": ["configureLogging", "getManager", "sleep", "TestingCrashManager"],
   "dbg-client.jsm": ["DebuggerTransport", "DebuggerClient", "RootClient", "LongStringClient", "EnvironmentClient", "ObjectClient"],
   "dbg-server.jsm": ["DebuggerServer", "ActorPool", "OriginalLocation"],
   "debug.js": ["NS_ASSERT"],