Add infrastructure for partial layouts

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index a5dddea9ff27a0d1ab8a4d19beb42ad0897e3fd2..5e0cb8ac994377e500eb8571d4c0b588555c7b2b 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -152,6 +152,7 @@
 #include "core/platform/DateComponents.h"
 #include "core/platform/HistogramSupport.h"
 #include "core/platform/Language.h"
+#include "core/platform/ScrollbarTheme.h"
 #include "core/platform/Timer.h"
 #include "core/platform/chromium/TraceEvent.h"
 #include "core/platform/network/HTTPParsers.h"
@@ -1747,6 +1748,9 @@ void Document::updateLayout()
     if (frameView && renderer() && (frameView->layoutPending() || renderer()->needsLayout()))
         frameView->layout();
 
+    if (frameView)
+        frameView->resetPartialLayoutState();
+
     setNeedsFocusedElementCheck();
 }
 
@@ -1759,37 +1763,69 @@ void Document::setNeedsFocusedElementCheck()
     m_didPostCheckFocusedElementTask = true;
 }
 
-// FIXME: This is a bad idea and needs to be removed eventually.
-// Other browsers load stylesheets before they continue parsing the web page.
-// Since we don't, we can run JavaScript code that needs answers before the
-// stylesheets are loaded. Doing a layout ignoring the pending stylesheets
-// lets us get reasonable answers. The long term solution to this problem is
-// to instead suspend JavaScript execution.
-void Document::updateLayoutIgnorePendingStylesheets()
+void Document::recalcStyleForLayoutIgnoringPendingStylesheets()
 {
-    bool oldIgnore = m_ignorePendingStylesheets;
-
     if (!haveStylesheetsLoaded()) {
         m_ignorePendingStylesheets = true;
-        // FIXME: We are willing to attempt to suppress painting with outdated style info only once.  Our assumption is that it would be
-        // dangerous to try to stop it a second time, after page content has already been loaded and displayed
-        // with accurate style information.  (Our suppression involves blanking the whole page at the
-        // moment.  If it were more refined, we might be able to do something better.)
-        // It's worth noting though that this entire method is a hack, since what we really want to do is
-        // suspend JS instead of doing a layout with inaccurate information.
+        // FIXME: We are willing to attempt to suppress painting with outdated style info only once.
+        // Our assumption is that it would be dangerous to try to stop it a second time, after page
+        // content has already been loaded and displayed with accurate style information. (Our
+        // suppression involves blanking the whole page at the moment. If it were more refined, we
+        // might be able to do something better.) It's worth noting though that this entire method
+        // is a hack, since what we really want to do is suspend JS instead of doing a layout with
+        // inaccurate information.
         HTMLElement* bodyElement = body();
         if (bodyElement && !bodyElement->renderer() && m_pendingSheetLayout == NoLayoutWithPendingSheets) {
             m_pendingSheetLayout = DidLayoutWithPendingSheets;
             styleResolverChanged(RecalcStyleImmediately);
         } else if (m_hasNodesWithPlaceholderStyle)
-            // If new nodes have been added or style recalc has been done with style sheets still pending, some nodes
-            // may not have had their real style calculated yet. Normally this gets cleaned when style sheets arrive
-            // but here we need up-to-date style immediately.
+            // If new nodes have been added or style recalc has been done with style sheets still
+            // pending, some nodes may not have had their real style calculated yet. Normally this
+            // gets cleaned when style sheets arrive but here we need up-to-date style immediately.
             recalcStyle(Force);
     }
+}
 
+// FIXME: This is a bad idea and needs to be removed eventually.
+// Other browsers load stylesheets before they continue parsing the web page.
+// Since we don't, we can run JavaScript code that needs answers before the
+// stylesheets are loaded. Doing a layout ignoring the pending stylesheets
+// lets us get reasonable answers. The long term solution to this problem is
+// to instead suspend JavaScript execution.
+void Document::updateLayoutIgnorePendingStylesheets()
+{
+    bool oldIgnore = m_ignorePendingStylesheets;

[esprehn, 2013/08/23 20:47:27]

You should switch this to a TemporaryChange<bool>

[pdr., 2013/08/26 05:50:40]

Done

+    recalcStyleForLayoutIgnoringPendingStylesheets();
     updateLayout();
+    m_ignorePendingStylesheets = oldIgnore;
+}
 
+void Document::partialUpdateLayoutIgnorePendingStylesheets(Node* stopLayoutAtNode)
+{
+    bool oldIgnore = m_ignorePendingStylesheets;

[esprehn, 2013/08/23 20:47:27]

Ditto

[pdr., 2013/08/26 05:50:40]

Done.

+    recalcStyleForLayoutIgnoringPendingStylesheets();
+
+    if (stopLayoutAtNode) {
+        // Non-overlay scrollbars can cause layout during layout.
+        // FIXME: REMOVE THIS 'true' BEFORE LANDING. This allows linux to run partiallayout
+        //        performance tests, even though it's only valid for OSX and Android.
+        if (true || ScrollbarTheme::theme()->usesOverlayScrollbars()) {
+            // FIXME: Text autosizing will not work with partial layout.
+            bool canPartialLayout = true;
+            RenderObject* renderer = stopLayoutAtNode->renderer();
+            while (renderer) {
+                if (!renderer->supportsPartialLayout()) {
+                    canPartialLayout = false;
+                    break;
+                }
+                renderer = renderer->parent();
+            }
+            if (canPartialLayout)
+                view()->setStopLayoutAtRenderer(stopLayoutAtNode->renderer());
+        }
+    }
+
+    updateLayout();
     m_ignorePendingStylesheets = oldIgnore;
 }