Initial ResizeObserver implementation

third_party/WebKit/Source/core/frame/FrameView.cpp

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index c62706460ec56341039e27ee288c1b63097793b0..5bc175fe1a86c581eb868922080103b0ac002f7b 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -37,6 +37,7 @@
 #include "core/editing/FrameSelection.h"
 #include "core/editing/RenderedPosition.h"
 #include "core/editing/markers/DocumentMarkerController.h"
+#include "core/events/ErrorEvent.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/frame/EventHandlerRegistry.h"
 #include "core/frame/FrameHost.h"
@@ -72,6 +73,7 @@
 #include "core/layout/svg/LayoutSVGRoot.h"
 #include "core/loader/FrameLoader.h"
 #include "core/loader/FrameLoaderClient.h"
+#include "core/observer/ResizeObserverController.h"
 #include "core/page/AutoscrollController.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/FocusController.h"
@@ -2445,6 +2447,38 @@ void FrameView::scheduleVisualUpdateForPaintInvalidationIfNeeded()
     // Otherwise the paint invalidation will be handled in paint invalidation phase of this cycle.
 }
 
+void FrameView::notifyResizeObserver()
+{
+    if (!m_frame->document()->resizeObserverController())
+        return;
+
+    ResizeObserverController& resizeController = m_frame->document()->ensureResizeObserverController();
+
+    DCHECK(lifecycle().state() >= DocumentLifecycle::LayoutClean);
+
+    size_t resizeNotifyCount = 0;
+
+    while (resizeController.gatherObservations()) {

[szager1, 2016/07/11 18:33:47]

This is a much clearer organization of the loop, thanks!

[atotic1, 2016/07/11 23:18:57]

Done.

+        if (++resizeNotifyCount > ResizeObserverController::kRenderLoopLimit) {
+            resizeController.clearObservations();
+            // Report the error.
+            ErrorEvent * error = ErrorEvent::create("ResizeObserver loop limit exceeded", SourceLocation::capture(m_frame->document()), nullptr);
+            m_frame->document()->reportException(error, NotSharableCrossOrigin);
+            // Ensure notifications will get delivered in next cycle.

[szager1, 2016/07/11 18:33:47]

This comment is obsolete, I think.  Maybe just something about scheduling a new
frame because at this point, the layout may be left in an inconsistent state.

[atotic1, 2016/07/11 23:18:58]

The comment is meaningful. Without scheduleAnimation(), notifications will not
get delivered until next redraw. I can remove the comment if you'd like.
I put the comment in because this was a bug fix I put in after a test failed.

[szager1, 2016/07/11 23:33:34]

But just a few lines up, you call resizeController.clearObservations().  So
presumably, at this point, there won't be any notifications left for next frame
(which is, I think, the right thing to do).

+            if (FrameView* frameView = m_frame->view())
+                frameView->scheduleAnimation();
+            break;
+        }
+
+        resizeController.deliverObservations();
+
+        if (lifecycle().state() < DocumentLifecycle::LayoutClean || layoutView()->needsLayout())
+            updateStyleAndLayoutIfNeededRecursive();
+    }
+
+    DCHECK(!layoutView()->needsLayout());
+}
+
 // TODO(leviw): We don't assert lifecycle information from documents in child PluginViews.
 void FrameView::updateLifecyclePhasesInternal(LifeCycleUpdateOption phases)
 {
@@ -2462,13 +2496,16 @@ void FrameView::updateLifecyclePhasesInternal(LifeCycleUpdateOption phases)
     }
 
     updateStyleAndLayoutIfNeededRecursive();
-    ASSERT(lifecycle().state() >= DocumentLifecycle::LayoutClean);
 
     if (phases == OnlyUpToLayoutClean) {
         updateViewportIntersectionsForSubtree(phases);
         return;
     }
 
+    notifyResizeObserver();

[szager1, 2016/07/11 18:33:47]

Are you sure we don't want to run this when (phases == OnlyUpToLayoutClean)? 
This begs the question: in a world with ResizeObserver, what do we mean by
"layout clean"?

[atotic1, 2016/07/11 23:18:57]

I believe that ResizeObserver should not run if phases == OnlyUpToLayoutClean
According to spec, ResizeObserver only notifies before paint. 
OnlyUpToLayoutClean does not paint.

I've looked at callers that trigger OnlyUpToLayoutClean condition, 
and only one is FrameSelection::unclippedBounds()

[szager1, 2016/07/11 23:33:34]

Good enough for me, I just wanted to make sure you were thinking about it.

+
+    DCHECK(lifecycle().state() >= DocumentLifecycle::LayoutClean);
+
     if (LayoutViewItem view = layoutViewItem()) {
         {
             TRACE_EVENT1("devtools.timeline", "UpdateLayerTree", "data", InspectorUpdateLayerTreeEvent::data(m_frame.get()));