Rewind the DocumentLifecycle when dirtying state

Source/core/dom/DocumentLifecycle.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 56 matching lines @@
 }
 
 DocumentLifecycle::~DocumentLifecycle()
 {
 }
 
 #if !ASSERT_DISABLED
 
 bool DocumentLifecycle::canAdvanceTo(State state) const
 {
-    // This transition is bogus, but we've whitelisted it anyway.
-    if (s_deprecatedTransitionStack && m_state == s_deprecatedTransitionStack->from() && state == s_deprecatedTransitionStack->to())
-        return true;
     if (state > m_state)
         return true;
     if (m_state == Disposed) {
         // FIXME: We can dispose a document multiple times. This seems wrong.
         // See https://code.google.com/p/chromium/issues/detail?id=301668.
         return state == Disposed;
     }
     if (m_state == StyleClean) {
-        if (state == StyleRecalcPending)
-            return true;
         // We can synchronously recalc style.
         if (state == InStyleRecalc)
             return true;
         // We can synchronously perform layout.
         if (state == InPreLayout)
             return true;
         if (state == InPerformLayout)
             return true;
         // We can redundant arrive in the style clean state.
         if (state == StyleClean)
@@ skipping 12 matching lines @@
     if (m_state == AfterPerformLayout) {
         if (state == InPreLayout)
             return true;
         // If we're doing a partial layout, we won't actually end up cleaning
         // out all the layout dirty bits. Instead, we'll return to StyleClean.
         if (state == StyleClean)
             return true;
         return false;
     }
     if (m_state == LayoutClean) {
-        if (state == StyleRecalcPending)
-            return true;
         // We can synchronously recalc style.
         if (state == InStyleRecalc)
             return true;
         // We can synchronously perform layout.
         if (state == InPreLayout)
             return true;
         if (state == InPerformLayout)
             return true;
         // We can redundant arrive in the layout clean state. This situation
         // can happen when we call layout recursively and we unwind the stack.
         if (state == LayoutClean)
             return true;
         if (state == StyleClean)
             return true;
         return false;
     }
     if (m_state == CompositingClean) {
-        if (state == StyleRecalcPending)
-            return true;
         if (state == InStyleRecalc)
             return true;
         if (state == InPreLayout)
             return true;
         if (state == InCompositingUpdate)
             return true;
         return false;
     }
     return false;
 }
 
+bool DocumentLifecycle::canRewindTo(State state) const
+{
+    // This transition is bogus, but we've whitelisted it anyway.
+    if (s_deprecatedTransitionStack && m_state == s_deprecatedTransitionStack->from() && state == s_deprecatedTransitionStack->to())
+        return true;
+    return m_state == StyleClean || m_state == AfterPerformLayout || m_state == LayoutClean || m_state == CompositingClean;
+}
+
 #endif
 
 void DocumentLifecycle::advanceTo(State state)
 {
     ASSERT(canAdvanceTo(state));
     m_state = state;
 }
 
+void DocumentLifecycle::ensureStateAtMost(State state)
+{
+    ASSERT(state == VisualUpdatePending || state == StyleClean || state == LayoutClean);
+    if (m_state <= state)
+        return;
+    ASSERT(canRewindTo(state));
+    m_state = state;
+}
+
 }