Add layout states to DocumentLifecycle state machine

Source/core/dom/DocumentLifecycle.cpp

Index: Source/core/dom/DocumentLifecycle.cpp
diff --git a/Source/core/dom/DocumentLifecycle.cpp b/Source/core/dom/DocumentLifecycle.cpp
index d53e0bc9bede645eb3c4b02477a488f283a14232..2f7b818d6452f29b99632b65407a514c14c64dfb 100644
--- a/Source/core/dom/DocumentLifecycle.cpp
+++ b/Source/core/dom/DocumentLifecycle.cpp
@@ -36,6 +36,32 @@
 
 namespace WebCore {
 
+static DocumentLifecycle::DeprecatedTransition* s_deprecatedTransitionStack = 0;
+
+DocumentLifecycle::Scope::Scope(DocumentLifecycle& lifecycle, State finalState)
+    : m_lifecycle(lifecycle)
+    , m_finalState(finalState)
+{
+}
+
+DocumentLifecycle::Scope::~Scope()
+{
+    m_lifecycle.advanceTo(m_finalState);
+}
+
+DocumentLifecycle::DeprecatedTransition::DeprecatedTransition(State from, State to)
+    : m_previous(s_deprecatedTransitionStack)
+    , m_from(from)
+    , m_to(to)
+{
+    s_deprecatedTransitionStack = this;
+}
+
+DocumentLifecycle::DeprecatedTransition::~DeprecatedTransition()
+{
+    s_deprecatedTransitionStack = m_previous;
+}
+
 DocumentLifecycle::DocumentLifecycle()
     : m_state(Uninitialized)
 {
@@ -45,34 +71,79 @@ 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;
-    // FIXME: We can dispose a document multiple times. This seems wrong.
-    // See https://code.google.com/p/chromium/issues/detail?id=301668.
-    if (m_state == Disposed)
+    if (m_state == Disposed) {

[ojan, 2014/02/07 02:08:46]

Nit: should these if-statements be a switch statement? Not sure it really
matters either way.

+        // 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 == Clean) {
-        // We can synchronously enter recalc style without rewinding to
-        // StyleRecalcPending.
-        return state == InStyleRecalc;
+    }
+    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.

[ojan, 2014/02/07 02:08:46]

This is a little weird to me. I guess Document::recalcStyle doesn't early return
if it doesn't need recalc.

[abarth-chromium, 2014/02/07 02:18:51]

Yeah.  It just doesn't do any work.

+        if (state == StyleClean)
+            return true;
+        return false;
+    }
+    if (m_state == InPreLayout) {
+        if (state == InStyleRecalc)
+            return true;
+        if (state == StyleClean)
+            return true;
+        if (state == InPreLayout)
+            return true;
+        return false;
+    }
+    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.

[ojan, 2014/02/07 02:08:46]

Ditto...FrameView::layout doesn't early return either.

[abarth-chromium, 2014/02/07 02:18:51]

It's because layout is recursive.  As you walk up the recursion, everything is
already clean.

+        if (state == LayoutClean)
+            return true;
+        return false;
     }
     return false;
 }
 
+#endif
+
 void DocumentLifecycle::advanceTo(State state)
 {
     ASSERT(canAdvanceTo(state));
     m_state = state;
 }
 
-void DocumentLifecycle::rewindTo(State state)
-{
-    ASSERT(m_state == Clean);
-    ASSERT(state < m_state);
-    m_state = state;
-    ASSERT(isActive());
-}
-
 }