Deferred frame loading stats v2

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 44f06f71c39688b9e294c312eb2d608559822fb4..4210de45ea123fec1ac9256627f56c2d4eccd135 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -4345,11 +4345,30 @@ void FrameView::updateViewportIntersectionIfNeeded() {
   m_viewportIntersectionValid = true;
   FrameView* parent = parentFrameView();
   if (!parent) {
+    // display:none frames have no parent because they're not in the DOM.

[dcheng, 2016/10/07 05:52:40]

I don't understand this comment in conjunction with the code below. I believe
what happens with display:none iframes is they end up attached to the frame tree
(this can be tested by appending a style="display:none" iframe to the DOM and
observing that window.lenght) increases). However, it's not in the layout tree
(see below)

+    if (HTMLFrameOwnerElement* element = frame().deprecatedLocalOwner()) {
+      if (const ComputedStyle* style = element->computedStyle()) {

[dgrogan, 2016/10/05 01:19:08]

I'm trying to detect when an iframe has style="display:none". But
element->computedStyle() always returns nullptr. Any ideas how I can access the
style from here? (It's also probably not a good sign that I'm using deprecated
stuff.)

[dcheng, 2016/10/07 05:52:40]

I think what's happening here is that there's no LayoutObject, so ComputedStyle
will always be null.

Maybe not having a LayoutObject is a good enough proxy for display:none? +timloh
who knows much more about CSS than me.

+        if (style->display() == EDisplay::None)
+          frame().document()->wouldLoadBecause(WouldLoadDisplayNone);
+      }
+    }
+    frame().document()->wouldLoadBecause(WouldLoadOutOfProcess);
     m_viewportIntersection = frameRect();
     return;
   }
   ASSERT(!parent->m_needsUpdateViewportIntersection);
 
+  bool parentLoaded = parent->frame().document()->wouldLoadReason() != Created;
+  if (parentLoaded) {
+    if (frameRect().isEmpty()) {
+      frame().document()->wouldLoadBecause(WouldLoadZeroByZero);
+    } else if (frameRect().maxY() < 0) {
+      frame().document()->wouldLoadBecause(WouldLoadAbove);
+    } else if (frameRect().maxX() < 0) {
+      frame().document()->wouldLoadBecause(WouldLoadLeft);
+    }
+  }
+
   // If our parent is hidden, then we are too.
   if (parent->m_viewportIntersection.isEmpty()) {
     m_viewportIntersection = parent->m_viewportIntersection;
@@ -4368,6 +4387,9 @@ void FrameView::updateViewportIntersectionIfNeeded() {
   // TODO(skyostil): Expand the viewport to make it less likely to see stale content while scrolling.
   IntRect viewport = parent->m_viewportIntersection;
   m_viewportIntersection.intersect(viewport);
+
+  if (parentLoaded && !m_viewportIntersection.isEmpty())
+    frame().document()->wouldLoadBecause(WouldLoadVisible);
 }
 
 void FrameView::updateViewportIntersectionsForSubtree(
@@ -4453,8 +4475,6 @@ void FrameView::notifyRenderThrottlingObservers() {
 
   updateThrottlingStatus();
 
-  frame().document()->onVisibilityMaybeChanged(!m_hiddenForThrottling);
-
   bool becameThrottled = !wasThrottled && canThrottleRendering();
   bool becameUnthrottled = wasThrottled && !canThrottleRendering();
   ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator();