Add infrastructure for partial layouts

Source/core/page/FrameView.cpp

Index: Source/core/page/FrameView.cpp
diff --git a/Source/core/page/FrameView.cpp b/Source/core/page/FrameView.cpp
index 8f0cb6b8f1cce3967d9ab878be73eeac73f4bdd7..45eebc74ba1cfa22ba083be51fd9c364a1670183 100644
--- a/Source/core/page/FrameView.cpp
+++ b/Source/core/page/FrameView.cpp
@@ -179,6 +179,8 @@ FrameView::FrameView(Frame* frame)
     , m_didRunAutosize(false)
     , m_hasSoftwareFilters(false)
     , m_visibleContentScaleFactor(1)
+    , m_shouldStopPartialLayout(false)
+    , m_stopLayoutAtRenderer(0)
 {
     init();
 
@@ -844,6 +846,14 @@ void FrameView::layout(bool allowSubtree)
     if (m_inLayout)
         return;
 
+    ASSERT(!shouldStopPartialLayout());
+    /*
+    if (shouldStopPartialLayout()) {
+        resetPartialLayoutState();
+        return;
+    }
+    */
+
     TRACE_EVENT0("webkit", "FrameView::layout");
     TRACE_EVENT_SCOPED_SAMPLING_STATE("Blink", "Layout");
 
@@ -1010,6 +1020,12 @@ void FrameView::layout(bool allowSubtree)
         m_layoutRoot = 0;
     } // Reset m_layoutSchedulingEnabled to its previous value.
 
+    if (shouldStopPartialLayout()) {
+        // Reset partial layout state post-layout.
+        resetPartialLayoutState();
+        return;
+    }
+
     bool neededFullRepaint = m_doFullRepaint;
 
     if (!inSubtreeLayout && !toRenderView(rootForThisLayout)->printing())
@@ -1035,9 +1051,22 @@ void FrameView::layout(bool allowSubtree)
         cache->postNotification(rootForThisLayout, AXObjectCache::AXLayoutComplete, true);
     updateAnnotatedRegions();
 
+    if (shouldStopPartialLayout()) {
+        // Reset partial layout state post-layout.
+        resetPartialLayoutState();
+        return;
+    }
+
     layoutLazyBlocks();
 
-    ASSERT(!rootForThisLayout->needsLayout());
+    if (shouldStopPartialLayout()) {
+        // Reset partial layout state post-layout.
+        resetPartialLayoutState();
+        return;
+    }
+
+    if (!shouldStopPartialLayout())
+        ASSERT(!rootForThisLayout->needsLayout());
 
     updateCanBlitOnScrollRecursively();
 
@@ -1079,11 +1108,16 @@ void FrameView::layout(bool allowSubtree)
         return;
 
 #ifndef NDEBUG
-    // Post-layout assert that nobody was re-marked as needing layout during layout.
-    for (RenderObject* renderer = document->renderer(); renderer; renderer = renderer->nextInPreOrder())
-        ASSERT(!renderer->needsLayout());
+    if (!shouldStopPartialLayout()) {
+        // Post-layout assert that nobody was re-marked as needing layout during layout.
+        for (RenderObject* renderer = document->renderer(); renderer; renderer = renderer->nextInPreOrder())
+            ASSERT(!renderer->needsLayout());
+    }
 #endif
 
+    // Reset partial layout state post-layout.
+    resetPartialLayoutState();
+
     // FIXME: It should be not possible to remove the FrameView from the frame/page during layout
     // however m_inLayout is not set for most of this function, so none of our RELEASE_ASSERTS
     // in Frame/Page will fire. One of the post-layout tasks is disconnecting the Frame from
@@ -1124,6 +1158,19 @@ void FrameView::layoutLazyBlocks()
     }
 }
 
+void FrameView::checkPartialLayoutComplete(RenderObject* renderer)
+{
+    ASSERT(renderer);
+    if (renderer == m_stopLayoutAtRenderer) {
+        // Make sure a partial layout was allowed.
+        do {
+            ASSERT(renderer->supportsPartialLayout());
+        } while ((renderer = renderer->parent()));
+
+        m_shouldStopPartialLayout = true;
+    }
+}
+
 RenderBox* FrameView::embeddedContentBox() const
 {
     RenderView* renderView = this->renderView();