Log to UMA why we would load a third-party frame

third_party/WebKit/Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 218 matching lines @@
   // Aliases by callers.
   // Clone a node: https://dom.spec.whatwg.org/#concept-node-clone
   CreatedByCloneNode = AsynchronousCustomElements,
   CreatedByImportNode = CreatedByCloneNode,
   // https://dom.spec.whatwg.org/#dom-document-createelement
   CreatedByCreateElement = SynchronousCustomElements,
   // https://html.spec.whatwg.org/#create-an-element-for-the-token
   CreatedByFragmentParser = CreatedByParser | AsynchronousCustomElements,
 };
 
+// Collect data about deferred loading of offscreen cross-origin documents. All
+// cross-origin documents log Created. Only those that would load log a reason.
+// We can then see the % of cross-origin documents that never have to load.
+// See https://crbug.com/635105.
+// Logged to UMA, don't re-arrange entries without creating a new histogram.
+enum WouldLoadReason {
+  Created,
+  // If outer and inner frames aren't in the same process we can't determine
+  // if the inner frame is visible, so just load it.
+  // TODO(dgrogan): Revisit after https://crbug.com/650433 is fixed.
+  WouldLoadOutOfProcess,
+  // The next four indicate frames that are probably used for cross-origin
+  // communication.
+  WouldLoadDisplayNone,
+  WouldLoadZeroByZero,
+  WouldLoadAbove,
+  WouldLoadLeft,
+  // We have to load documents in visible frames.
+  WouldLoadVisible,
+
+  WouldLoadReasonEnd
+};
+
 using DocumentClassFlags = unsigned char;
 
 class CORE_EXPORT Document : public ContainerNode,
                              public TreeScope,
                              public SecurityContext,
                              public ExecutionContext,
                              public Supplementable<Document> {
   DEFINE_WRAPPERTYPEINFO();
   USING_GARBAGE_COLLECTED_MIXIN(Document);
 
@@ skipping 1030 matching lines @@
   }
 
   Element* rootScroller() const;
   void setRootScroller(Element*, ExceptionState&);
   RootScrollerController* rootScrollerController() const {
     return m_rootScrollerController.get();
   }
 
   bool isInMainFrame() const;
 
-  void onVisibilityMaybeChanged(bool visible);
+  void maybeRecordLoadReason(WouldLoadReason);
+  WouldLoadReason wouldLoadReason() { return m_wouldLoadReason; }
 
   PropertyRegistry* propertyRegistry();
 
  protected:
   Document(const DocumentInit&, DocumentClassFlags = DefaultDocumentClass);
 
   void didUpdateSecurityOrigin() final;
 
   void clearXMLVersion() { m_xmlVersion = String(); }
 
@@ skipping 334 matching lines @@
   Member<IntersectionObserverController> m_intersectionObserverController;
   Member<NodeIntersectionObserverData> m_intersectionObserverData;
   Member<ResizeObserverController> m_resizeObserverController;
 
   int m_nodeCount;
 
   bool m_mayContainV0Shadow = false;
 
   Member<SnapCoordinator> m_snapCoordinator;
 
-  bool m_visibilityWasLogged;
+  WouldLoadReason m_wouldLoadReason;
 
   Member<PropertyRegistry> m_propertyRegistry;
 };
 
 extern template class CORE_EXTERN_TEMPLATE_EXPORT Supplement<Document>;
 
 inline bool Document::shouldOverrideLegacyDescription(
     ViewportDescription::Type origin) const {
   // The different (legacy) meta tags have different priorities based on the
   // type regardless of which order they appear in the DOM. The priority is
@@ skipping 36 matching lines @@
 DEFINE_TYPE_CASTS(TreeScope, Document, document, true, true);
 
 }  // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLiveDocumentInstances();
 #endif
 
 #endif  // Document_h