Add infrastructure for partial layouts

Source/core/rendering/SubtreeLayoutScope.cpp

Index: Source/core/rendering/SubtreeLayoutScope.cpp
diff --git a/Source/core/rendering/SubtreeLayoutScope.cpp b/Source/core/rendering/SubtreeLayoutScope.cpp
index c3bfefe745a64383618009fb6e6b9e43b7744e81..fbc0c76cbad825080afd37890e5d4ff8365cf823 100644
--- a/Source/core/rendering/SubtreeLayoutScope.cpp
+++ b/Source/core/rendering/SubtreeLayoutScope.cpp
@@ -44,17 +44,19 @@ SubtreeLayoutScope::SubtreeLayoutScope(RenderObject* root)
 
 SubtreeLayoutScope::~SubtreeLayoutScope()
 {
-    RELEASE_ASSERT(!m_root->needsLayout());
+    if (!m_root->document()->view()->shouldStopPartialLayout()) {

[esprehn, 2013/08/18 03:43:15]

This should be an early return.

[pdr., 2013/08/20 06:19:10]

Done.

+        RELEASE_ASSERT(!m_root->needsLayout());
 
 #ifndef NDEBUG
-    for (HashSet<RenderObject*>::iterator it = m_renderersToLayout.begin(); it != m_renderersToLayout.end(); ++it) {
-        RenderObject* renderer = *it;
-        // FIXME: Thie patter is really common. Move it into an assertRendererLaidOut function.
-        if (renderer->needsLayout())
-            showRenderTree(renderer);
-        ASSERT(!renderer->needsLayout());
-    }
+        for (HashSet<RenderObject*>::iterator it = m_renderersToLayout.begin(); it != m_renderersToLayout.end(); ++it) {
+            RenderObject* renderer = *it;
+            // FIXME: Thie patter is really common. Move it into an assertRendererLaidOut function.
+            if (renderer->needsLayout())
+                showRenderTree(renderer);
+            ASSERT(!renderer->needsLayout());
+        }
 #endif
+    }
 }
 
 void SubtreeLayoutScope::setNeedsLayout(RenderObject* descendant)