Log to UMA when x-origin frames (1) are created and (2) become visible

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

Index: third_party/WebKit/Source/core/frame/LocalFrame.cpp
diff --git a/third_party/WebKit/Source/core/frame/LocalFrame.cpp b/third_party/WebKit/Source/core/frame/LocalFrame.cpp
index 57c4765081cc252bb1073a41379e3bf0d86f6413..2c34bdccc8e5ff0afe7a95ca276f629ac3800160 100644
--- a/third_party/WebKit/Source/core/frame/LocalFrame.cpp
+++ b/third_party/WebKit/Source/core/frame/LocalFrame.cpp
@@ -69,6 +69,7 @@
 #include "core/paint/TransformRecorder.h"
 #include "core/svg/SVGDocumentExtensions.h"
 #include "platform/DragImage.h"
+#include "platform/Histogram.h"
 #include "platform/JSONValues.h"
 #include "platform/PluginScriptForbiddenScope.h"
 #include "platform/RuntimeEnabledFeatures.h"
@@ -217,6 +218,21 @@ inline float parentTextZoomFactor(LocalFrame* frame)
     return toLocalFrame(parent)->textZoomFactor();
 }
 
+// These are logged to UMA, so don't re-arrange them without creating a new histogram.
+enum FrameStateForDeferredLoading {
+    Created,
+    WouldLoadBecauseVisible,
+    // TODO(dgrogan): Add WouldLoadBecauseTopOrLeft, WouldLoadBecauseDisplayNone, etc
+
+    FrameStateForDeferredLoadingEnd
+};
+
+void RecordStateToHistogram(FrameStateForDeferredLoading state)
+{
+    DEFINE_STATIC_LOCAL(EnumerationHistogram, unseenFrameHistogram, ("FrameLoading.Deferred.StateCountsV1", FrameStateForDeferredLoadingEnd));
+    unseenFrameHistogram.count(state);
+}
+
 } // namespace
 
 template class CORE_TEMPLATE_EXPORT Supplement<LocalFrame>;
@@ -806,6 +822,8 @@ inline LocalFrame::LocalFrame(FrameLoaderClient* client, FrameHost* host, FrameO
     , m_textZoomFactor(parentTextZoomFactor(this))
     , m_inViewSourceMode(false)
     , m_interfaceProvider(interfaceProvider)
+    , m_visibilityWasLogged(false)
+    , m_creationWasLogged(false)
 {
     if (isLocalRoot())
         m_instrumentingAgents = new InstrumentingAgents();
@@ -837,6 +855,23 @@ PluginData* LocalFrame::pluginData() const
     return page()->pluginData();
 }
 
+void LocalFrame::didInstallNewDocument()
+{
+    if (!m_creationWasLogged && isCrossOriginSubframe()) {

[dgrogan, 2016/08/19 23:56:23]

installNewDocument is called twice when an iframe is first created (at least
when it is created with a srcdoc) so I had to keep
LocalFrame::m_creationWasLogged, but the current solution is still better than
having to check m_creationWasLogged every time the visibility might have
changed.

[dcheng, 2016/08/22 07:00:29]

When a frame is first created, it always starts on the initial empty document
(https://html.spec.whatwg.org/multipage/browsers.html#initialise-the-document-...
kind of references this). So what happens is the initial empty document is
created and installed first, then the Document for the srcdoc is created and
installed.

Can we use FrameLoaderStateMachine::creatingInitialEmptyDocument() or
isDisplayingInitialEmptyDocument() to distinguish between these cases? I'm
guessing we don't want to record the UMA for the initial empty document.

[dgrogan, 2016/08/22 23:38:09]

You're right. This function is now only called when
committedFirstRealDocumentLoad() is true.

+        m_creationWasLogged = true;
+        RecordStateToHistogram(Created);
+    }
+}
+
+void LocalFrame::onVisibilityMaybeChanged(bool visible)
+{
+    if (visible && !m_visibilityWasLogged && isCrossOriginSubframe()) {
+        DCHECK(m_creationWasLogged);

[dgrogan, 2016/08/22 23:38:09]

This was racy.

+        m_visibilityWasLogged = true;
+        RecordStateToHistogram(WouldLoadBecauseVisible);
+    }
+}
+
 DEFINE_WEAK_IDENTIFIER_MAP(LocalFrame);
 
 FrameNavigationDisabler::FrameNavigationDisabler(LocalFrame& frame)