diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index 723471ebb21c..c5fb8eecec98 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -3178,12 +3178,20 @@ nsJSContext::ClearScope(void *aGlobalObj, PRBool aClearFromProtoChain)
       JS_ClearPendingException(mContext);
     }
 
-    if (!JS_ClearScope(mContext, obj))
-      JS_ClearPendingException(mContext);
+    // Hack fix for bug 611653. Originally, this always called JS_ClearScope,
+    // which was required to avoid leaks. But for native objects, the JS
+    // engine has an optimization that requires that permanent properties of
+    // the global object are never deleted. So instead, we call a new special
+    // API that clears the values of the global, thus avoiding leaks without
+    // deleting any properties.
+    if (obj->isNative()) {
+      js_UnbrandAndClearSlots(mContext, obj);
+    } else {
+      JS_ClearScope(mContext, obj);
+    }
 
     if (xpc::WrapperFactory::IsXrayWrapper(obj)) {
-      if (!JS_ClearScope(mContext, &obj->getProxyExtra().toObject()))
-        JS_ClearPendingException(mContext);
+      JS_ClearScope(mContext, &obj->getProxyExtra().toObject());
     }
 
     if (window != JSVAL_VOID) {
@@ -3221,8 +3229,7 @@ nsJSContext::ClearScope(void *aGlobalObj, PRBool aClearFromProtoChain)
       // Clear up obj's prototype chain, but not Object.prototype.
       for (JSObject *o = ::JS_GetPrototype(mContext, obj), *next;
            o && (next = ::JS_GetPrototype(mContext, o)); o = next)
-        if (!::JS_ClearScope(mContext, o))
-          JS_ClearPendingException(mContext);
+        ::JS_ClearScope(mContext, o);
     }
   }
 
diff --git a/ipc/testshell/XPCShellEnvironment.cpp b/ipc/testshell/XPCShellEnvironment.cpp
index db6b071beaf5..de0d2c1a4bec 100644
--- a/ipc/testshell/XPCShellEnvironment.cpp
+++ b/ipc/testshell/XPCShellEnvironment.cpp
@@ -524,8 +524,7 @@ Clear(JSContext *cx,
 {
     jsval *argv = JS_ARGV(cx, vp);
     if (argc > 0 && !JSVAL_IS_PRIMITIVE(argv[0])) {
-        if (!JS_ClearScope(cx, JSVAL_TO_OBJECT(argv[0])))
-	    return JS_FALSE;
+        JS_ClearScope(cx, JSVAL_TO_OBJECT(argv[0]));
     } else {
         JS_ReportError(cx, "'clear' requires an object");
         return JS_FALSE;
diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index b7813e11e1a3..b843178cd3cb 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -3922,14 +3922,12 @@ JS_DeleteProperty(JSContext *cx, JSObject *obj, const char *name)
     return JS_DeleteProperty2(cx, obj, name, &junk);
 }
 
-JS_PUBLIC_API(JSBool)
+JS_PUBLIC_API(void)
 JS_ClearScope(JSContext *cx, JSObject *obj)
 {
     CHECK_REQUEST(cx);
     assertSameCompartment(cx, obj);
 
-    uint32 span = obj->slotSpan();
-
     JSFinalizeOp clearOp = obj->getOps()->clear;
     if (clearOp)
         clearOp(cx, obj);
@@ -3937,36 +3935,16 @@ JS_ClearScope(JSContext *cx, JSObject *obj)
     if (obj->isNative())
         js_ClearNative(cx, obj);
 
-    js_InitRandom(cx);
-
     /* Clear cached class objects on the global object. */
     if (obj->isGlobal()) {
-        if (!obj->unbrand(cx))
-            return false;
-
         for (int key = JSProto_Null; key < JSProto_LIMIT * 3; key++)
             JS_SetReservedSlot(cx, obj, key, JSVAL_VOID);
 
-        /* Clear regexp statics. */
-        RegExpStatics::extractFrom(obj)->clear();
-
         /* Clear the CSP eval-is-allowed cache. */
         JS_SetReservedSlot(cx, obj, JSRESERVED_GLOBAL_EVAL_ALLOWED, JSVAL_VOID);
-
-        /*
-         * Compile-and-go scripts might rely on these slots to be present,
-         * so set a bunch of dummy properties to make sure compiled code
-         * doesn't reach into empty space.
-         */
-        uint32 n = 0;
-        while (obj->slotSpan() < span) {
-            if (!JS_DefinePropertyById(cx, obj, INT_TO_JSID(n), JSVAL_VOID, NULL, NULL, 0))
-                return false;
-            ++n;
-        }
     }
 
-    return true;
+    js_InitRandom(cx);
 }
 
 JS_PUBLIC_API(JSIdArray *)
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 6586e859505b..91af9067ccf8 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -2469,7 +2469,7 @@ JS_DeleteElement(JSContext *cx, JSObject *obj, jsint index);
 extern JS_PUBLIC_API(JSBool)
 JS_DeleteElement2(JSContext *cx, JSObject *obj, jsint index, jsval *rval);
 
-extern JS_PUBLIC_API(JSBool)
+extern JS_PUBLIC_API(void)
 JS_ClearScope(JSContext *cx, JSObject *obj);
 
 extern JS_PUBLIC_API(JSIdArray *)
diff --git a/js/src/jscompartment.cpp b/js/src/jscompartment.cpp
index 24c239f25ea0..972117f3e4a6 100644
--- a/js/src/jscompartment.cpp
+++ b/js/src/jscompartment.cpp
@@ -270,14 +270,8 @@ JSCompartment::wrap(JSContext *cx, Value *vp)
     /* If we already have a wrapper for this value, use it. */
     if (WrapperMap::Ptr p = crossCompartmentWrappers.lookup(*vp)) {
         *vp = p->value;
-        if (vp->isObject()) {
-            JSObject *obj = &vp->toObject();
-            do {
-                JS_ASSERT(obj->isWrapper());
-                obj->setParent(global);
-                obj = obj->getProto();
-            } while (obj);
-        }
+        if (vp->isObject())
+            vp->toObject().setParent(global);
         return true;
     }
 
diff --git a/js/src/jsobj.cpp b/js/src/jsobj.cpp
index 292e1f397851..68c30377387c 100644
--- a/js/src/jsobj.cpp
+++ b/js/src/jsobj.cpp
@@ -4450,6 +4450,40 @@ JSObject::freeSlot(JSContext *cx, uint32 slot)
     return false;
 }
 
+JS_FRIEND_API(void)
+js_UnbrandAndClearSlots(JSContext *cx, JSObject *obj)
+{
+    JS_ASSERT(obj->isNative());
+    JS_ASSERT(obj->isGlobal());
+
+    /* This can return false but that doesn't mean it failed. */
+    obj->unbrand(cx);
+
+    /*
+     * Clear the prototype cache. We must not clear the other global
+     * reserved slots, as other code will crash if they are arbitrarily
+     * reset (e.g., regexp statics).
+     */
+    for (int key = JSProto_Null; key < JSRESERVED_GLOBAL_THIS; key++)
+        JS_SetReservedSlot(cx, obj, key, JSVAL_VOID);
+
+    /*
+     * Clear the non-reserved slots.
+     */
+    ClearValueRange(obj->slots + JSCLASS_RESERVED_SLOTS(obj->clasp),
+                    obj->capacity - JSCLASS_RESERVED_SLOTS(obj->clasp),
+                    obj->clasp == &js_ArrayClass);
+
+    /*
+     * We just overwrote all slots to undefined, so the freelist has
+     * been trashed. We need to clear the head pointer or else we will
+     * crash later. This leaks slots but the object is all but dead
+     * anyway.
+     */
+    if (obj->hasPropertyTable())
+        obj->lastProperty()->getTable()->freelist = SHAPE_INVALID_SLOT;
+}
+
 /* JSBOXEDWORD_INT_MAX as a string */
 #define JSBOXEDWORD_INT_MAX_STRING "1073741823"
 
diff --git a/js/src/jsobj.h b/js/src/jsobj.h
index 9bdd4f9008f2..55190c8d1357 100644
--- a/js/src/jsobj.h
+++ b/js/src/jsobj.h
@@ -1768,6 +1768,15 @@ extern JSBool
 js_SetNativeAttributes(JSContext *cx, JSObject *obj, js::Shape *shape,
                        uintN attrs);
 
+/*
+ * Hack fix for bug 611653: Do not use for any other purpose.
+ *
+ * Unbrand and set all slot values to undefined (except reserved slots that
+ * are not used for cached prototypes).
+ */
+JS_FRIEND_API(void)
+js_UnbrandAndClearSlots(JSContext *cx, JSObject *obj);
+
 namespace js {
 
 /*
diff --git a/js/src/jsscope.h b/js/src/jsscope.h
index 99aefa13a336..1c297367c525 100644
--- a/js/src/jsscope.h
+++ b/js/src/jsscope.h
@@ -297,6 +297,7 @@ struct Shape : public JSObjectMap
     friend class js::PropertyTree;
     friend class js::Bindings;
     friend bool IsShapeAboutToBeFinalized(JSContext *cx, const js::Shape *shape);
+    friend JS_FRIEND_API(void) ::js_UnbrandAndClearSlots(JSContext *cx, JSObject *obj);
 
     /* 
      * numLinearSearches starts at zero and is incremented initially on each
diff --git a/js/src/shell/js.cpp b/js/src/shell/js.cpp
index 72bd14578058..f2e156485588 100644
--- a/js/src/shell/js.cpp
+++ b/js/src/shell/js.cpp
@@ -2733,11 +2733,10 @@ Clear(JSContext *cx, uintN argc, jsval *vp)
 {
     JSObject *obj;
     if (argc != 0 && !JS_ValueToObject(cx, JS_ARGV(cx, vp)[0], &obj))
-        return false;
-    if (!JS_ClearScope(cx, obj))
-        return false;
+        return JS_FALSE;
+    JS_ClearScope(cx, obj);
     JS_SET_RVAL(cx, vp, JSVAL_VOID);
-    return true;
+    return JS_TRUE;
 }
 
 static JSBool
@@ -4685,8 +4684,7 @@ split_setup(JSContext *cx, JSBool evalcx)
         }
     }
 
-    if (!JS_ClearScope(cx, outer))
-        return NULL;
+    JS_ClearScope(cx, outer);
 
 #ifndef LAZY_STANDARD_CLASSES
     if (!JS_InitStandardClasses(cx, inner))
diff --git a/js/src/xpconnect/loader/mozJSComponentLoader.h b/js/src/xpconnect/loader/mozJSComponentLoader.h
index adfe1d1b3e2b..120a951add88 100644
--- a/js/src/xpconnect/loader/mozJSComponentLoader.h
+++ b/js/src/xpconnect/loader/mozJSComponentLoader.h
@@ -178,8 +178,7 @@ class mozJSComponentLoader : public mozilla::ModuleLoader,
                 JSAutoEnterCompartment ac;
                 ac.enterAndIgnoreErrors(sSelf->mContext, global);
 
-                if (!JS_ClearScope(sSelf->mContext, global))
-                    JS_ClearPendingException(sSelf->mContext);
+                JS_ClearScope(sSelf->mContext, global);
                 JS_RemoveObjectRoot(sSelf->mContext, &global);
             }
 
diff --git a/js/src/xpconnect/shell/xpcshell.cpp b/js/src/xpconnect/shell/xpcshell.cpp
index 22466bb493b5..334a396d98f9 100644
--- a/js/src/xpconnect/shell/xpcshell.cpp
+++ b/js/src/xpconnect/shell/xpcshell.cpp
@@ -679,8 +679,7 @@ static JSBool
 Clear(JSContext *cx, uintN argc, jsval *vp)
 {
     if (argc > 0 && !JSVAL_IS_PRIMITIVE(JS_ARGV(cx, vp)[0])) {
-        if (!JS_ClearScope(cx, JSVAL_TO_OBJECT(JS_ARGV(cx, vp)[0])))
-            return JS_FALSE;
+        JS_ClearScope(cx, JSVAL_TO_OBJECT(JS_ARGV(cx, vp)[0]));
     } else {
         JS_ReportError(cx, "'clear' requires an object");
         return JS_FALSE;
@@ -2020,8 +2019,7 @@ main(int argc, char **argv)
                         (void**) getter_AddRefs(bogus));
 #endif
             JSPRINCIPALS_DROP(cx, gJSPrincipals);
-            if (!JS_ClearScope(cx, glob))
-                NS_ERROR("clearing scope failed");
+            JS_ClearScope(cx, glob);
             JS_GC(cx);
             JSContext *oldcx;
             cxstack->Pop(&oldcx);
diff --git a/js/src/xpconnect/src/dom_quickstubs.qsconf b/js/src/xpconnect/src/dom_quickstubs.qsconf
index 08e9f0d8df74..1dd1728a3d11 100644
--- a/js/src/xpconnect/src/dom_quickstubs.qsconf
+++ b/js/src/xpconnect/src/dom_quickstubs.qsconf
@@ -558,9 +558,8 @@ nsIDOMHTMLDocument_Write_customMethodCallCode = """
 
 nsIDOMStorage_Clear_customMethodCallCode = """
     rv = self->Clear();
-    if (NS_SUCCEEDED(rv)) {
-        rv = JS_ClearScope(cx, obj) ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
-    }
+    if (NS_SUCCEEDED(rv))
+        JS_ClearScope(cx, obj);
 """
 
 CUSTOM_QS = {
diff --git a/js/src/xpconnect/tests/TestXPC.cpp b/js/src/xpconnect/tests/TestXPC.cpp
index 45fc3b661a71..a088de45e106 100644
--- a/js/src/xpconnect/tests/TestXPC.cpp
+++ b/js/src/xpconnect/tests/TestXPC.cpp
@@ -856,8 +856,7 @@ int main()
 
         {
             JSAutoRequest ar(jscontext);
-            if (!JS_ClearScope(jscontext, glob))
-                DIE("FAILED to clear scope");
+            JS_ClearScope(jscontext, glob);
             JS_GC(jscontext);
             JS_GC(jscontext);
         }