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 6361e0b757baafd17193c2be49401f50519cb66e..fcdb9d91f9faae35c587794634688b53bf04f795 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_canStopPartialLayout(false)
+    , m_stopLayoutAtRenderer(0)
 {
     init();
 
@@ -844,6 +846,12 @@ void FrameView::layout(bool allowSubtree)
     if (m_inLayout)
         return;
 
+    if (m_canStopPartialLayout) {
+        resetPartialLayoutState();
+        return;
+    }
+    //ASSERT(!m_canStopPartialLayout);
+
     TRACE_EVENT0("webkit", "FrameView::layout");
     TRACE_EVENT_SCOPED_SAMPLING_STATE("Blink", "Layout");
 
@@ -1010,6 +1018,12 @@ void FrameView::layout(bool allowSubtree)
         m_layoutRoot = 0;
     } // Reset m_layoutSchedulingEnabled to its previous value.
 
+    if (m_canStopPartialLayout) {
+        // Reset partial layout state post-layout.
+        resetPartialLayoutState();
+        return;
+    }
+
     bool neededFullRepaint = m_doFullRepaint;
 
     if (!inSubtreeLayout && !toRenderView(rootForThisLayout)->printing())
@@ -1035,9 +1049,22 @@ void FrameView::layout(bool allowSubtree)
         cache->postNotification(rootForThisLayout, AXObjectCache::AXLayoutComplete, true);
     updateAnnotatedRegions();
 
+    if (m_canStopPartialLayout) {
+        // Reset partial layout state post-layout.
+        resetPartialLayoutState();
+        return;
+    }
+
     layoutLazyBlocks();
 
-    ASSERT(!rootForThisLayout->needsLayout());
+    if (m_canStopPartialLayout) {
+        // Reset partial layout state post-layout.
+        resetPartialLayoutState();
+        return;
+    }
+
+    if (!m_canStopPartialLayout)
+        ASSERT(!rootForThisLayout->needsLayout());
 
     updateCanBlitOnScrollRecursively();
 
@@ -1079,11 +1106,16 @@ 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 (!m_canStopPartialLayout) {
+        // 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 +1156,15 @@ void FrameView::layoutLazyBlocks()
     }
 }
 
+void FrameView::checkPartialLayoutComplete(RenderObject* renderer)
+{
+    if (renderer == m_stopLayoutAtRenderer) {
+        //fprintf(stderr, "stopping partial layout!\n");
+        //BACKTRACE();
+        m_canStopPartialLayout = true;
+    }
+}
+
 RenderBox* FrameView::embeddedContentBox() const
 {
     RenderView* renderView = this->renderView();