Cross-origin iframes: collect data under hypothetical loading strategies

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

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index 7c6b7c7b85c9a21233639f5db59e26d86cc91183..d34bf21210e4a5784a43082aeed605238abe056e 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -407,7 +407,7 @@ static void runAutofocusTask(ExecutionContext* context) {
 static void recordLoadReasonToHistogram(WouldLoadReason reason) {
   DEFINE_STATIC_LOCAL(
       EnumerationHistogram, unseenFrameHistogram,
-      ("Navigation.DeferredDocumentLoading.StatesV3", WouldLoadReasonEnd));
+      ("Navigation.DeferredDocumentLoading.StatesV4", WouldLoadReasonEnd));
   unseenFrameHistogram.count(reason);
 }
 
@@ -504,7 +504,7 @@ Document::Document(const DocumentInit& initializer,
       m_hasViewportUnits(false),
       m_parserSyncPolicy(AllowAsynchronousParsing),
       m_nodeCount(0),
-      m_wouldLoadReason(Created),
+      m_wouldLoadReason(Invalid),
       m_passwordCount(0) {
   if (m_frame) {
     DCHECK(m_frame->page());
@@ -6402,13 +6402,16 @@ DEFINE_TRACE(Document) {
   SynchronousMutationNotifier::trace(visitor);
 }
 
-void Document::maybeRecordLoadReason(WouldLoadReason reason) {
-  DCHECK(m_wouldLoadReason == Created || reason != Created);
+void Document::recordDeferredLoadReason(WouldLoadReason reason) {
+  DCHECK(m_wouldLoadReason == Invalid || reason != Created);
+  DCHECK(reason != Invalid);
   DCHECK(frame());
-  if (m_wouldLoadReason == Created && frame()->isCrossOriginSubframe() &&
-      frame()->loader().stateMachine()->committedFirstRealDocumentLoad()) {
-    recordLoadReasonToHistogram(reason);
-  }
+  DCHECK(frame()->isCrossOriginSubframe());
+  if (reason <= m_wouldLoadReason ||
+      !frame()->loader().stateMachine()->committedFirstRealDocumentLoad())
+    return;
+  for (int i = m_wouldLoadReason + 1; i <= reason; ++i)

[ojan, 2016/11/22 00:41:59]

I think this means that passing WouldLoadNoParent would make it so that all of
the other WouldLoad* reasons would get set as well. Is that what you're
intending?

[dgrogan, 2016/11/29 00:57:32]

Intentional; it's simpler to subtract in the postprocessing step than it is to
make this code do something smarter. But changing from manhattan distance will
make this code more complicated so it might make sense to go ahead and give
WouldLoadNoParent special treatment here.

+    recordLoadReasonToHistogram(static_cast<WouldLoadReason>(i));
   m_wouldLoadReason = reason;
 }