From 830e3d549bce716a64c289fc5d59201b2629bd8b Mon Sep 17 00:00:00 2001
From: Gijs Kruitbosch <gijskruitbosch@gmail.com>
Date: Wed, 28 Oct 2009 22:44:15 +0100
Subject: [PATCH] Prepare callsites of clearUserPref so it can go back to
 throwing. r=gavin

---
 browser/base/content/openLocationLastURL.jsm               | 3 ++-
 .../test/browser/browser_privatebrowsing_opendir.js        | 3 ++-
 toolkit/mozapps/downloads/src/DownloadLastDir.jsm          | 2 +-
 toolkit/mozapps/extensions/content/extensions.js           | 3 ++-
 toolkit/mozapps/extensions/src/nsExtensionManager.js.in    | 7 ++++---
 5 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/browser/base/content/openLocationLastURL.jsm b/browser/base/content/openLocationLastURL.jsm
index 437797ddd1c2..dc7a111bf24d 100644
--- a/browser/base/content/openLocationLastURL.jsm
+++ b/browser/base/content/openLocationLastURL.jsm
@@ -88,7 +88,8 @@ let gOpenLocationLastURL = {
     }
   },
   reset: function() {
-    prefSvc.clearUserPref(LAST_URL_PREF);
+    if (prefSvc.prefHasUserValue(LAST_URL_PREF))
+        prefSvc.clearUserPref(LAST_URL_PREF);
     gOpenLocationLastURLData = "";
   }
 };
diff --git a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_opendir.js b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_opendir.js
index cb83edf610fa..475bd7ba866a 100644
--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_opendir.js
+++ b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_opendir.js
@@ -54,7 +54,8 @@ function test() {
 
   function setupCleanSlate() {
     gLastOpenDirectory.reset();
-    gPrefService.clearUserPref(kPrefName);
+    if (gPrefService.prefHasUserValue(kPrefName))
+        gPrefService.clearUserPref(kPrefName);
   }
 
   setupCleanSlate();
diff --git a/toolkit/mozapps/downloads/src/DownloadLastDir.jsm b/toolkit/mozapps/downloads/src/DownloadLastDir.jsm
index cac427e206dd..0f81be579277 100644
--- a/toolkit/mozapps/downloads/src/DownloadLastDir.jsm
+++ b/toolkit/mozapps/downloads/src/DownloadLastDir.jsm
@@ -97,7 +97,7 @@ let gDownloadLastDir = {
     } else {
       if (val instanceof Components.interfaces.nsIFile)
         prefSvc.setComplexValue(LAST_DIR_PREF, nsILocalFile, val);
-      else
+      else if (prefSvc.prefHasUserValue(LAST_DIR_PREF))
         prefSvc.clearUserPref(LAST_DIR_PREF);
     }
   }
diff --git a/toolkit/mozapps/extensions/content/extensions.js b/toolkit/mozapps/extensions/content/extensions.js
index 33384f59bc23..b40712e5b318 100644
--- a/toolkit/mozapps/extensions/content/extensions.js
+++ b/toolkit/mozapps/extensions/content/extensions.js
@@ -2238,7 +2238,8 @@ const gLWThemeObserver = {
     }
     else if (aTopic == "lightweight-theme-changed") {
       gLWThemeToSelect = LightweightThemeManager.currentTheme;
-      gPref.clearUserPref(PREF_LWTHEME_TO_SELECT);
+      if (gPref.prefHasUserValue(PREF_LWTHEME_TO_SELECT))
+          gPref.clearUserPref(PREF_LWTHEME_TO_SELECT);
     }
   }
 };
diff --git a/toolkit/mozapps/extensions/src/nsExtensionManager.js.in b/toolkit/mozapps/extensions/src/nsExtensionManager.js.in
index e2dd27e7dc41..ce8598f3a4f2 100644
--- a/toolkit/mozapps/extensions/src/nsExtensionManager.js.in
+++ b/toolkit/mozapps/extensions/src/nsExtensionManager.js.in
@@ -2316,7 +2316,8 @@ ExtensionManager.prototype = {
         // If we've changed to a non-default theme make sure there is no
         // lightweight theme selected
         if (toSelect != gDefaultTheme) {
-          gPref.clearUserPref(PREF_LWTHEME_TO_SELECT);
+          if (gPref.prefHasUserValue(PREF_LWTHEME_TO_SELECT))
+            gPref.clearUserPref(PREF_LWTHEME_TO_SELECT);
           LightweightThemeManager.currentTheme = null;
         }
       }
@@ -3311,8 +3312,8 @@ ExtensionManager.prototype = {
         // Remember the list of add-ons that were disabled this time around
         gPref.setCharPref(PREF_EM_DISABLED_ADDONS_LIST, disabledAddons.join(","));
       }
-    } else {
-      // Clear the disabled addons list
+    } else if (gPref.prefHasUserValue(PREF_EM_DISABLED_ADDONS_LIST)) {
+      // Clear the disabled addons list if necessary
       gPref.clearUserPref(PREF_EM_DISABLED_ADDONS_LIST);
     }