Add support for entering/exiting HTML fullscreen from OOPIFs.

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

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 4ae2e5d3a125ab92f99efd46fe859e6352e0f4ae..a8c4f22deedc3affe8824223d999c0eb9b0b6174 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -3059,7 +3059,22 @@ void Element::setContainsFullScreenElement(bool flag)
 static Element* parentCrossingFrameBoundaries(Element* element)
 {
     DCHECK(element);
-    return element->parentElement() ? element->parentElement() : element->document().localOwner();
+    if (element->parentElement())
+        return element->parentElement();
+
+    Frame* frame = element->document().frame();
+    if (!frame || !frame->owner())
+        return nullptr;
+
+    // Find the next LocalFrame on the ancestor chain, and return the
+    // corresponding <iframe> element for the remote child if it exists.
+    while (frame->tree().parent() && frame->tree().parent()->isRemoteFrame())
+        frame = frame->tree().parent();
+
+    if (frame->owner() && frame->owner()->isLocal())
+        return toHTMLFrameOwnerElement(frame->owner());
+
+    return nullptr;
 }
 
 void Element::setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries(bool flag)