Revert of Add ScriptForbiddenScope to weak callbacks of DOM wrappers

Source/core/dom/ScriptForbiddenScope.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/dom/ScriptForbiddenScope.h"
 
 #include "wtf/Assertions.h"
 #include "wtf/MainThread.h"
 
 namespace WebCore {
 
 #if ASSERT_ENABLED
 
 static unsigned s_scriptForbiddenCount = 0;
 
 ScriptForbiddenScope::ScriptForbiddenScope()
 {
-    // FIXME: Support non-main threads.
-    if (isMainThread())
-        ++s_scriptForbiddenCount;
+    ASSERT(isMainThread());
+    ++s_scriptForbiddenCount;
 }
 
 ScriptForbiddenScope::~ScriptForbiddenScope()
 {
-    if (isMainThread())
-        --s_scriptForbiddenCount;
+    ASSERT(isMainThread());
+    --s_scriptForbiddenCount;
 }
 
 bool ScriptForbiddenScope::isScriptForbidden()
 {
     return isMainThread() && s_scriptForbiddenCount;
 }
 
 ScriptForbiddenScope::AllowUserAgentScript::AllowUserAgentScript()
     : m_change(s_scriptForbiddenCount, 0)
 {
 }
 
 ScriptForbiddenScope::AllowUserAgentScript::~AllowUserAgentScript()
 {
     ASSERT(!s_scriptForbiddenCount);
 }
 
 #endif
 
 } // namespace WebCore