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 a6bb610babb780280fcf39cf137b8ba0ac760691..1389af419b410bb57c0d971105d06dfa71e3bb13 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();
 
@@ -846,6 +848,8 @@ void FrameView::layout(bool allowSubtree)
     if (m_inLayout)
         return;
 
+    ASSERT(!shouldStopPartialLayout());
+
     TRACE_EVENT0("webkit", "FrameView::layout");
     TRACE_EVENT_SCOPED_SAMPLING_STATE("Blink", "Layout");
 
@@ -983,6 +987,14 @@ void FrameView::layout(bool allowSubtree)
 
         m_actionScheduler->pause();
 
+        // Text Autosizing requires two-pass layout which is incompatible with partial layout. If

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

This should be a FIXME for text autosizing not to do that.

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

Added fixme and a reference to crbug.com/256657.

+        // enabled, only do partial layout for the second layout.
+        RenderObject* delayPartialLayoutForRenderer = 0;
+        if (m_frame && m_frame->settings() && m_frame->settings()->textAutosizingEnabled()) {

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

m_frame cannot be null here. I'm pretty sure that'd be catastrophic to do layout
on a frameless document.

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

Done.

+            delayPartialLayoutForRenderer = m_stopLayoutAtRenderer;
+            m_stopLayoutAtRenderer = 0;
+        }
+
         {
             bool disableLayoutState = false;
             if (inSubtreeLayout) {
@@ -997,6 +1009,11 @@ void FrameView::layout(bool allowSubtree)
             forceLayoutParentViewIfNeeded();
             rootForThisLayout->layout();
 
+            // If text autosizing is enabled, do a partial layout for the second layout.
+            if (delayPartialLayoutForRenderer) {
+                ASSERT(!shouldStopPartialLayout());
+                m_stopLayoutAtRenderer = delayPartialLayoutForRenderer;
+            }
             bool autosized = document->textAutosizer()->processSubtree(rootForThisLayout);
             if (autosized && rootForThisLayout->needsLayout()) {
                 TRACE_EVENT0("webkit", "2nd layout due to Text Autosizing");
@@ -1012,6 +1029,13 @@ void FrameView::layout(bool allowSubtree)
         m_layoutRoot = 0;
     } // Reset m_layoutSchedulingEnabled to its previous value.
 
+    // Reset partial layout state post-layout and exit here if a partial layout was done.
+    if (shouldStopPartialLayout()) {
+        resetPartialLayoutState();
+        return;
+    }
+    resetPartialLayoutState();
+
     bool neededFullRepaint = m_doFullRepaint;
 
     if (!inSubtreeLayout && !toRenderView(rootForThisLayout)->printing())
@@ -1095,6 +1119,19 @@ void FrameView::layout(bool allowSubtree)
         frame()->page()->chrome().client()->layoutUpdated(frame());
 }
 
+void FrameView::checkPartialLayoutComplete(RenderObject* renderer)

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

This check should be inline.

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

Done.

+{
+    ASSERT(renderer);
+    if (renderer == m_stopLayoutAtRenderer) {
+        // Make sure a partial layout was allowed.
+        do {
+            ASSERT(renderer->supportsPartialLayout());
+        } while ((renderer = renderer->parent()));

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

Why do you need to check this twice? Doing it either before or after should be
enough?

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

The supportsPartialLayout loop was intended to just be an assert. I've cleaned
this up like so:
1) I've inlined checkPartialLayoutComplete and changed it to return a bool if
layout is complete.
2) I've moved the assertion loop behind an #ifndef NDEBUG check and into a
private function "checkPartialLayoutAllowed". The purpose of
checkPartialLayoutAllowed is just to assert that everything is working properly.

+
+        m_shouldStopPartialLayout = true;
+    }
+}
+
 RenderBox* FrameView::embeddedContentBox() const
 {
     RenderView* renderView = this->renderView();