--- a/browser/components/downloads/DownloadsCommon.jsm
+++ b/browser/components/downloads/DownloadsCommon.jsm
@@ -66,18 +66,16 @@ XPCOMUtils.defineLazyGetter(this, "Downl
   let { ConsoleAPI } = Cu.import("resource://gre/modules/Console.jsm", {});
   let consoleOptions = {
     maxLogLevelPref: "browser.download.loglevel",
     prefix: "Downloads"
   };
   return new ConsoleAPI(consoleOptions);
 });
 
-const nsIDM = Ci.nsIDownloadManager;
-
 const kDownloadsStringBundleUrl =
   "chrome://browser/locale/downloads/downloads.properties";
 
 const kDownloadsStringsRequiringFormatting = {
   sizeWithUnits: true,
   shortTimeLeftSeconds: true,
   shortTimeLeftMinutes: true,
   shortTimeLeftHours: true,
@@ -134,16 +132,29 @@ PrefObserver.register({
 
 // DownloadsCommon
 
 /**
  * This object is exposed directly to the consumers of this JavaScript module,
  * and provides shared methods for all the instances of the user interface.
  */
 this.DownloadsCommon = {
+  // The following legacy constants are still returned by stateOfDownload, but
+  // individual properties of the Download object should normally be used.
+  DOWNLOAD_NOTSTARTED: -1,
+  DOWNLOAD_DOWNLOADING: 0,
+  DOWNLOAD_FINISHED: 1,
+  DOWNLOAD_FAILED: 2,
+  DOWNLOAD_CANCELED: 3,
+  DOWNLOAD_PAUSED: 4,
+  DOWNLOAD_BLOCKED_PARENTAL: 6,
+  DOWNLOAD_DIRTY: 8,
+  DOWNLOAD_BLOCKED_POLICY: 9,
+
+  // The following are the possible values of the "attention" property.
   ATTENTION_NONE: "",
   ATTENTION_SUCCESS: "success",
   ATTENTION_WARNING: "warning",
   ATTENTION_SEVERE: "severe",
 
   /**
    * This can be used by add-on experiments as a killswitch for the new style
    * progress indication. This will be removed in bug 1329109 after the new
@@ -292,37 +303,37 @@ this.DownloadsCommon = {
   _privateSummary: null,
 
   /**
    * Returns the legacy state integer value for the provided Download object.
    */
   stateOfDownload(download) {
     // Collapse state using the correct priority.
     if (!download.stopped) {
-      return nsIDM.DOWNLOAD_DOWNLOADING;
+      return DownloadsCommon.DOWNLOAD_DOWNLOADING;
     }
     if (download.succeeded) {
-      return nsIDM.DOWNLOAD_FINISHED;
+      return DownloadsCommon.DOWNLOAD_FINISHED;
     }
     if (download.error) {
       if (download.error.becauseBlockedByParentalControls) {
-        return nsIDM.DOWNLOAD_BLOCKED_PARENTAL;
+        return DownloadsCommon.DOWNLOAD_BLOCKED_PARENTAL;
       }
       if (download.error.becauseBlockedByReputationCheck) {
-        return nsIDM.DOWNLOAD_DIRTY;
+        return DownloadsCommon.DOWNLOAD_DIRTY;
       }
-      return nsIDM.DOWNLOAD_FAILED;
+      return DownloadsCommon.DOWNLOAD_FAILED;
     }
     if (download.canceled) {
       if (download.hasPartialData) {
-        return nsIDM.DOWNLOAD_PAUSED;
+        return DownloadsCommon.DOWNLOAD_PAUSED;
       }
-      return nsIDM.DOWNLOAD_CANCELED;
+      return DownloadsCommon.DOWNLOAD_CANCELED;
     }
-    return nsIDM.DOWNLOAD_NOTSTARTED;
+    return DownloadsCommon.DOWNLOAD_NOTSTARTED;
   },
 
   /**
    * Helper function required because the Downloads Panel and the Downloads View
    * don't share the controller yet.
    */
   removeAndFinalizeDownload(download) {
     Downloads.getList(Downloads.ALL)

--- a/browser/components/downloads/DownloadsViewUI.jsm
+++ b/browser/components/downloads/DownloadsViewUI.jsm
@@ -320,28 +320,28 @@ this.DownloadsViewUI.DownloadElementShel
   /**
    * Returns the name of the default command to use for the current state of the
    * download, when there is a double click or another default interaction. If
    * there is no default command for the current state, returns an empty string.
    * The commands are implemented as functions on this object or derived ones.
    */
   get currentDefaultCommandName() {
     switch (DownloadsCommon.stateOfDownload(this.download)) {
-      case Ci.nsIDownloadManager.DOWNLOAD_NOTSTARTED:
+      case DownloadsCommon.DOWNLOAD_NOTSTARTED:
         return "downloadsCmd_cancel";
-      case Ci.nsIDownloadManager.DOWNLOAD_FAILED:
-      case Ci.nsIDownloadManager.DOWNLOAD_CANCELED:
+      case DownloadsCommon.DOWNLOAD_FAILED:
+      case DownloadsCommon.DOWNLOAD_CANCELED:
         return "downloadsCmd_retry";
-      case Ci.nsIDownloadManager.DOWNLOAD_PAUSED:
+      case DownloadsCommon.DOWNLOAD_PAUSED:
         return "downloadsCmd_pauseResume";
-      case Ci.nsIDownloadManager.DOWNLOAD_FINISHED:
+      case DownloadsCommon.DOWNLOAD_FINISHED:
         return "downloadsCmd_open";
-      case Ci.nsIDownloadManager.DOWNLOAD_BLOCKED_PARENTAL:
+      case DownloadsCommon.DOWNLOAD_BLOCKED_PARENTAL:
         return "downloadsCmd_openReferrer";
-      case Ci.nsIDownloadManager.DOWNLOAD_DIRTY:
+      case DownloadsCommon.DOWNLOAD_DIRTY:
         return "downloadsCmd_showBlockedInfo";
     }
     return "";
   },
 
   /**
    * Returns true if the specified command can be invoked on the current item.
    * The commands are implemented as functions on this object or derived ones.

--- a/browser/components/downloads/content/allDownloadsViewOverlay.js
+++ b/browser/components/downloads/content/allDownloadsViewOverlay.js
@@ -25,18 +25,16 @@ XPCOMUtils.defineLazyModuleGetter(this, 
                                   "resource://gre/modules/Promise.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "RecentWindow",
                                   "resource:///modules/RecentWindow.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Services",
                                   "resource://gre/modules/Services.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Task",
                                   "resource://gre/modules/Task.jsm");
 
-const nsIDM = Ci.nsIDownloadManager;
-
 const DESTINATION_FILE_URI_ANNO  = "downloads/destinationFileURI";
 const DOWNLOAD_META_DATA_ANNO    = "downloads/metaData";
 
 /**
  * Represents a download from the browser history. It implements part of the
  * interface of the Download object.
  *
  * @param aPlacesNode
@@ -67,27 +65,27 @@ HistoryDownload.prototype = {
       this.target.path = Cc["@mozilla.org/network/protocol;1?name=file"]
                            .getService(Ci.nsIFileProtocolHandler)
                            .getFileFromURLSpec(metaData.targetFileSpec).path;
     } catch (ex) {
       this.target.path = undefined;
     }
 
     if ("state" in metaData) {
-      this.succeeded = metaData.state == nsIDM.DOWNLOAD_FINISHED;
-      this.canceled = metaData.state == nsIDM.DOWNLOAD_CANCELED ||
-                      metaData.state == nsIDM.DOWNLOAD_PAUSED;
+      this.succeeded = metaData.state == DownloadsCommon.DOWNLOAD_FINISHED;
+      this.canceled = metaData.state == DownloadsCommon.DOWNLOAD_CANCELED ||
+                      metaData.state == DownloadsCommon.DOWNLOAD_PAUSED;
       this.endTime = metaData.endTime;
 
       // Recreate partial error information from the state saved in history.
-      if (metaData.state == nsIDM.DOWNLOAD_FAILED) {
+      if (metaData.state == DownloadsCommon.DOWNLOAD_FAILED) {
         this.error = { message: "History download failed." };
-      } else if (metaData.state == nsIDM.DOWNLOAD_BLOCKED_PARENTAL) {
+      } else if (metaData.state == DownloadsCommon.DOWNLOAD_BLOCKED_PARENTAL) {
         this.error = { becauseBlockedByParentalControls: true };
-      } else if (metaData.state == nsIDM.DOWNLOAD_DIRTY) {
+      } else if (metaData.state == DownloadsCommon.DOWNLOAD_DIRTY) {
         this.error = {
           becauseBlockedByReputationCheck: true,
           reputationCheckVerdict: metaData.reputationCheckVerdict || "",
         };
       } else {
         this.error = null;
       }
 

--- a/browser/components/downloads/test/browser/browser_basic_functionality.js
+++ b/browser/components/downloads/test/browser/browser_basic_functionality.js
@@ -9,21 +9,21 @@ registerCleanupFunction(function*() {
 
 /**
  * Make sure the downloads panel can display items in the right order and
  * contains the expected data.
  */
 add_task(function* test_basic_functionality() {
   // Display one of each download state.
   const DownloadData = [
-    { state: nsIDM.DOWNLOAD_NOTSTARTED },
-    { state: nsIDM.DOWNLOAD_PAUSED },
-    { state: nsIDM.DOWNLOAD_FINISHED },
-    { state: nsIDM.DOWNLOAD_FAILED },
-    { state: nsIDM.DOWNLOAD_CANCELED },
+    { state: DownloadsCommon.DOWNLOAD_NOTSTARTED },
+    { state: DownloadsCommon.DOWNLOAD_PAUSED },
+    { state: DownloadsCommon.DOWNLOAD_FINISHED },
+    { state: DownloadsCommon.DOWNLOAD_FAILED },
+    { state: DownloadsCommon.DOWNLOAD_CANCELED },
   ];
 
   // Wait for focus first
   yield promiseFocus();
 
   // Ensure that state is reset in case previous tests didn't finish.
   yield task_resetState();
 

--- a/browser/components/downloads/test/browser/browser_downloads_panel_block.js
+++ b/browser/components/downloads/test/browser/browser_downloads_panel_block.js
@@ -134,17 +134,17 @@ function promisePanelHidden() {
     DownloadsPanel.panel.addEventListener("popuphidden", function() {
       setTimeout(resolve, 0);
     }, {once: true});
   });
 }
 
 function makeDownload(verdict) {
   return {
-    state: nsIDM.DOWNLOAD_DIRTY,
+    state: DownloadsCommon.DOWNLOAD_DIRTY,
     hasBlockedData: true,
     errorObj: {
       result: Components.results.NS_ERROR_FAILURE,
       message: "Download blocked.",
       becauseBlocked: true,
       becauseBlockedByReputationCheck: true,
       reputationCheckVerdict:  verdict,
     },

--- a/browser/components/downloads/test/browser/browser_downloads_panel_footer.js
+++ b/browser/components/downloads/test/browser/browser_downloads_panel_footer.js
@@ -29,36 +29,36 @@ add_task(function* test_openDownloadsFol
   });
 
   yield task_resetState();
 });
 
 add_task(function* test_clearList() {
   const kTestCases = [{
     downloads: [
-      { state: nsIDM.DOWNLOAD_NOTSTARTED },
-      { state: nsIDM.DOWNLOAD_FINISHED },
-      { state: nsIDM.DOWNLOAD_FAILED },
-      { state: nsIDM.DOWNLOAD_CANCELED },
+      { state: DownloadsCommon.DOWNLOAD_NOTSTARTED },
+      { state: DownloadsCommon.DOWNLOAD_FINISHED },
+      { state: DownloadsCommon.DOWNLOAD_FAILED },
+      { state: DownloadsCommon.DOWNLOAD_CANCELED },
     ],
     expectClearListShown: true,
     expectedItemNumber: 0,
   }, {
     downloads: [
-      { state: nsIDM.DOWNLOAD_NOTSTARTED },
-      { state: nsIDM.DOWNLOAD_FINISHED },
-      { state: nsIDM.DOWNLOAD_FAILED },
-      { state: nsIDM.DOWNLOAD_PAUSED },
-      { state: nsIDM.DOWNLOAD_CANCELED },
+      { state: DownloadsCommon.DOWNLOAD_NOTSTARTED },
+      { state: DownloadsCommon.DOWNLOAD_FINISHED },
+      { state: DownloadsCommon.DOWNLOAD_FAILED },
+      { state: DownloadsCommon.DOWNLOAD_PAUSED },
+      { state: DownloadsCommon.DOWNLOAD_CANCELED },
     ],
     expectClearListShown: true,
     expectedItemNumber: 1,
   }, {
     downloads: [
-      { state: nsIDM.DOWNLOAD_PAUSED },
+      { state: DownloadsCommon.DOWNLOAD_PAUSED },
     ],
     expectClearListShown: false,
     expectedItemNumber: 1,
   }];
 
   for (let testCase of kTestCases) {
     yield verify_clearList(testCase);
   }

--- a/browser/components/downloads/test/browser/browser_downloads_panel_height.js
+++ b/browser/components/downloads/test/browser/browser_downloads_panel_height.js
@@ -5,17 +5,17 @@
 
 /**
  * This test exists because we use a <panelmultiview> element and it handles
  * some of the height changes for us. We need to verify that the height is
  * updated correctly if downloads are removed while the panel is hidden.
  */
 add_task(function* test_height_reduced_after_removal() {
   yield task_addDownloads([
-    { state: nsIDM.DOWNLOAD_FINISHED },
+    { state: DownloadsCommon.DOWNLOAD_FINISHED },
   ]);
 
   yield task_openPanel();
   let panel = document.getElementById("downloadsPanel");
   let heightBeforeRemoval = panel.getBoundingClientRect().height;
 
   // We want to close the panel before we remove the download from the list.
   DownloadsPanel.hidePanel();

--- a/browser/components/downloads/test/browser/head.js
+++ b/browser/components/downloads/test/browser/head.js
@@ -19,18 +19,16 @@ XPCOMUtils.defineLazyModuleGetter(this, 
                                   "resource://gre/modules/Promise.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Task",
                                   "resource://gre/modules/Task.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
                                   "resource://gre/modules/PlacesUtils.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "HttpServer",
     "resource://testing-common/httpd.js");
 
-const nsIDM = Ci.nsIDownloadManager;
-
 var gTestTargetFile = FileUtils.getFile("TmpD", ["dm-ui-test.file"]);
 gTestTargetFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, FileUtils.PERMS_FILE);
 
 // Load mocking/stubbing library, sinon
 // docs: http://sinonjs.org/docs/
 /* global sinon:false */
 Services.scriptloader.loadSubScript("resource://testing-common/sinon-1.16.1.js");
 
@@ -158,21 +156,22 @@ function* task_addDownloads(aItems) {
   for (let item of aItems) {
     let download = {
       source: {
         url: "http://www.example.com/test-download.txt",
       },
       target: {
         path: gTestTargetFile.path,
       },
-      succeeded: item.state == nsIDM.DOWNLOAD_FINISHED,
-      canceled: item.state == nsIDM.DOWNLOAD_CANCELED ||
-                item.state == nsIDM.DOWNLOAD_PAUSED,
-      error: item.state == nsIDM.DOWNLOAD_FAILED ? new Error("Failed.") : null,
-      hasPartialData: item.state == nsIDM.DOWNLOAD_PAUSED,
+      succeeded: item.state == DownloadsCommon.DOWNLOAD_FINISHED,
+      canceled: item.state == DownloadsCommon.DOWNLOAD_CANCELED ||
+                item.state == DownloadsCommon.DOWNLOAD_PAUSED,
+      error: item.state == DownloadsCommon.DOWNLOAD_FAILED ?
+             new Error("Failed.") : null,
+      hasPartialData: item.state == DownloadsCommon.DOWNLOAD_PAUSED,
       hasBlockedData: item.hasBlockedData || false,
       startTime: new Date(startTimeMs++),
     };
     // `"errorObj" in download` must be false when there's no error.
     if (item.errorObj) {
       download.errorObj = item.errorObj;
     }
     yield publicList.add(yield Downloads.createDownload(download));