--- a/browser/base/content/browser-context.inc
+++ b/browser/base/content/browser-context.inc
@@ -377,17 +377,17 @@
                 accesskey="&viewPartialSourceCmd.accesskey;"
                 oncommand="gContextMenu.viewPartialSource('mathml');"
                 observes="isImage"/>
       <menuseparator id="context-sep-viewsource"/>
       <menuitem id="context-viewsource"
                 label="&viewPageSourceCmd.label;"
                 accesskey="&viewPageSourceCmd.accesskey;"
                 oncommand="BrowserViewSource(gContextMenu.browser);"
-                observes="canViewSource"/>
+                observes="isImage"/>
       <menuitem id="context-viewinfo"
                 label="&viewPageInfoCmd.label;"
                 accesskey="&viewPageInfoCmd.accesskey;"
                 oncommand="gContextMenu.viewInfo();"/>
       <menuseparator id="spell-separator"/>
       <menuitem id="spell-check-enabled"
                 label="&spellCheckToggle.label;"
                 type="checkbox"

--- a/browser/base/content/browser-sets.inc
+++ b/browser/base/content/browser-sets.inc
@@ -34,17 +34,17 @@
     <command id="cmd_closeWindow" oncommand="BrowserTryToCloseWindow()" reserved="true"/>
     <command id="cmd_toggleMute" oncommand="gBrowser.selectedTab.toggleMuteAudio()"/>
     <command id="cmd_CustomizeToolbars" oncommand="BrowserCustomizeToolbar()"/>
     <command id="cmd_quitApplication" oncommand="goQuitApplication()" reserved="true"/>
 
 
     <commandset id="editMenuCommands"/>
 
-    <command id="View:PageSource" oncommand="BrowserViewSource(window.gBrowser.selectedBrowser);" observes="canViewSource"/>
+    <command id="View:PageSource" oncommand="BrowserViewSource(window.gBrowser.selectedBrowser);" observes="isImage"/>
     <command id="View:PageInfo" oncommand="BrowserPageInfo();"/>
     <command id="View:FullScreen" oncommand="BrowserFullScreen();"/>
     <command id="View:ReaderView" oncommand="ReaderParent.toggleReaderMode(event);"/>
     <command id="cmd_find"
              oncommand="gFindBar.onFindCommand();"
              observes="isImage"/>
     <command id="cmd_findAgain"
              oncommand="gFindBar.onFindAgainCommand(false);"
@@ -169,17 +169,16 @@
                  accesskey="&editPopupSettings.accesskey;"
                  oncommand="gPopupBlockerObserver.editPopupSettings();"/>
     <broadcaster id="blockedPopupDontShowMessage"
                  accesskey="&dontShowMessage.accesskey;"
                  type="checkbox"
                  oncommand="gPopupBlockerObserver.dontShowMessage();"/>
     <broadcaster id="blockedPopupsSeparator"/>
     <broadcaster id="isImage"/>
-    <broadcaster id="canViewSource"/>
     <broadcaster id="isFrameImage"/>
     <broadcaster id="singleFeedMenuitemState" disabled="true"/>
     <broadcaster id="multipleFeedsMenuState" hidden="true"/>
     <broadcaster id="tabviewGroupsNumber" groups="1"/>
 #ifdef MOZ_SERVICES_SYNC
     <broadcaster id="sync-setup-state"/>
     <broadcaster id="sync-syncnow-state" hidden="true"/>
     <broadcaster id="sync-reauth-state" hidden="true"/>
@@ -227,19 +226,17 @@
                  key="key_responsiveUI"/>
     <broadcaster id="devtoolsMenuBroadcaster_Eyedropper"
                  label="&eyedropper.label;"
                  type="checkbox" autocheck="false"
                  command="Tools:Eyedropper"/>
     <broadcaster id="devtoolsMenuBroadcaster_PageSource"
                  label="&pageSourceCmd.label;"
                  key="key_viewSource"
-                 command="View:PageSource">
-      <observes element="canViewSource" attribute="disabled"/>
-    </broadcaster>
+                 command="View:PageSource"/>
     <broadcaster id="devtoolsMenuBroadcaster_ErrorConsole"
                  label="&errorConsoleCmd.label;"
                  command="Tools:ErrorConsole"/>
     <broadcaster id="devtoolsMenuBroadcaster_GetMoreTools"
                  label="&getMoreDevtoolsCmd.label;"
                  oncommand="openUILinkIn('https://addons.mozilla.org/firefox/collections/mozilla/webdeveloper/', 'tab');"/>
     <broadcaster id="devtoolsMenuBroadcaster_connect"
                  label="&devtoolsConnect.label;"

--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -4044,20 +4044,16 @@ var XULBrowserWindow = {
   },
   get statusTextField () {
     return gBrowser.getStatusPanel();
   },
   get isImage () {
     delete this.isImage;
     return this.isImage = document.getElementById("isImage");
   },
-  get canViewSource () {
-    delete this.canViewSource;
-    return this.canViewSource = document.getElementById("canViewSource");
-  },
 
   init: function () {
     // Initialize the security button's state and tooltip text.
     var securityUI = gBrowser.securityUI;
     this.onSecurityChange(null, null, securityUI.state, true);
   },
 
   setJSStatus: function () {
@@ -4205,53 +4201,41 @@ var XULBrowserWindow = {
     }
     else if (aStateFlags & nsIWebProgressListener.STATE_STOP) {
       // This (thanks to the filter) is a network stop or the last
       // request stop outside of loading the document, stop throbbers
       // and progress bars and such
       if (aRequest) {
         let msg = "";
         let location;
-        let canViewSource = true;
         // Get the URI either from a channel or a pseudo-object
         if (aRequest instanceof nsIChannel || "URI" in aRequest) {
           location = aRequest.URI;
 
           // For keyword URIs clear the user typed value since they will be changed into real URIs
           if (location.scheme == "keyword" && aWebProgress.isTopLevel)
             gBrowser.userTypedValue = null;
 
-          canViewSource = !Services.prefs.getBoolPref("view_source.tab") ||
-                          location.scheme != "view-source";
-
           if (location.spec != "about:blank") {
             switch (aStatus) {
               case Components.results.NS_ERROR_NET_TIMEOUT:
                 msg = gNavigatorBundle.getString("nv_timeout");
                 break;
             }
           }
         }
 
         this.status = "";
         this.setDefaultStatus(msg);
 
         // Disable menu entries for images, enable otherwise
-        if (browser.documentContentType && BrowserUtils.mimeTypeIsTextBased(browser.documentContentType)) {
+        if (browser.documentContentType && BrowserUtils.mimeTypeIsTextBased(browser.documentContentType))
           this.isImage.removeAttribute('disabled');
-        } else {
-          canViewSource = false;
+        else
           this.isImage.setAttribute('disabled', 'true');
-        }
-
-        if (canViewSource) {
-          this.canViewSource.removeAttribute('disabled');
-        } else {
-          this.canViewSource.setAttribute('disabled', 'true');
-        }
       }
 
       this.isBusy = false;
 
       if (this._busyUI) {
         this._busyUI = false;
 
         this.stopCommand.setAttribute("disabled", "true");

--- a/browser/base/content/test/general/browser.ini
+++ b/browser/base/content/test/general/browser.ini
@@ -470,17 +470,16 @@ skip-if = os == "linux" || e10s # Bug 10
 [browser_urlbarSearchSingleWordNotification.js]
 [browser_urlbarSearchSuggestionsNotification.js]
 [browser_urlbarStop.js]
 [browser_urlbarTrimURLs.js]
 [browser_urlbar_autoFill_backspaced.js]
 [browser_urlbar_search_healthreport.js]
 [browser_urlbar_searchsettings.js]
 [browser_utilityOverlay.js]
-[browser_viewSourceInTabOnViewSource.js]
 [browser_visibleFindSelection.js]
 [browser_visibleLabel.js]
 [browser_visibleTabs.js]
 [browser_visibleTabs_bookmarkAllPages.js]
 skip-if = true # Bug 1005420 - fails intermittently. also with e10s enabled: bizarre problem with hidden tab having _mouseenter called, via _setPositionalAttributes, and tab not being found resulting in 'candidate is undefined'
 [browser_visibleTabs_bookmarkAllTabs.js]
 [browser_visibleTabs_contextMenu.js]
 [browser_visibleTabs_tabPreview.js]

deleted file mode 100644
--- a/browser/base/content/test/general/browser_viewSourceInTabOnViewSource.js
+++ /dev/null
@@ -1,31 +0,0 @@
-add_task(function*() {
-  yield new Promise((resolve) => {
-    SpecialPowers.pushPrefEnv({"set": [
-                                ["view_source.tab", true],
-                              ]}, resolve);
-  });
-});
-
-add_task(function* test_regular_page() {
-  function* test_expect_view_source_enabled(browser) {
-    ok(!XULBrowserWindow.canViewSource.hasAttribute("disabled"),
-       "View Source should be enabled");
-  }
-
-  yield BrowserTestUtils.withNewTab({
-    gBrowser,
-    url: "http://example.com",
-  }, test_expect_view_source_enabled);
-});
-
-add_task(function* test_view_source_page() {
-  function* test_expect_view_source_disabled(browser) {
-    ok(XULBrowserWindow.canViewSource.hasAttribute("disabled"),
-       "View Source should be disabled");
-  }
-
-  yield BrowserTestUtils.withNewTab({
-    gBrowser,
-    url: "view-source:http://example.com",
-  }, test_expect_view_source_disabled);
-});