Track connected subframes per-Document instead of per-Node.

third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.cpp b/third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.cpp
index 45cf6917e7ef553671e5368311fd6165371e64b3..9cba72e0fc09f9e30bc56ef05e29d760eebf8cd8 100644
--- a/third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.cpp
@@ -153,11 +153,10 @@ void HTMLFrameOwnerElement::setContentFrame(Frame& frame)
     // Make sure we will not end up with two frames referencing the same owner element.
     ASSERT(!m_contentFrame || m_contentFrame->owner() != this);
     // Disconnected frames should not be allowed to load.
-    ASSERT(inDocument());
-    m_contentFrame = &frame;
+    ASSERT(inActiveDocument());
 
-    for (ContainerNode* node = this; node; node = node->parentOrShadowHostNode())
-        node->incrementConnectedSubframeCount();
+    m_contentFrame = &frame;
+    document().subframeTracker().connectSubframe(*this);
 }
 
 void HTMLFrameOwnerElement::clearContentFrame()
@@ -165,10 +164,10 @@ void HTMLFrameOwnerElement::clearContentFrame()
     if (!m_contentFrame)
         return;
 
+    // If there's a connected content frame, the parent frame must be active.
+    ASSERT(inActiveDocument());
     m_contentFrame = nullptr;
-
-    for (ContainerNode* node = this; node; node = node->parentOrShadowHostNode())
-        node->decrementConnectedSubframeCount();
+    document().subframeTracker().disconnectSubframe(*this);
 }
 
 void HTMLFrameOwnerElement::disconnectContentFrame()