Revert of Add ScriptForbiddenScope to weak callbacks of DOM wrappers

Source/core/dom/ScriptForbiddenScope.cpp

Index: Source/core/dom/ScriptForbiddenScope.cpp
diff --git a/Source/core/dom/ScriptForbiddenScope.cpp b/Source/core/dom/ScriptForbiddenScope.cpp
index c7e164cd548c4393cff14b40a5dd82f19903c301..81540dcb6f3ea68c3cd0d9ca2190b87b46401610 100644
--- a/Source/core/dom/ScriptForbiddenScope.cpp
+++ b/Source/core/dom/ScriptForbiddenScope.cpp
@@ -16,15 +16,14 @@
 
 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()