Propagate inert state to OOPIFs when a modal dialog is active

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

Index: third_party/WebKit/Source/core/html/HTMLDialogElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLDialogElement.cpp b/third_party/WebKit/Source/core/html/HTMLDialogElement.cpp
index 1d9e1a693d6210291de5c0bb9ecfeb98bd34a60c..3a89cb9840495b448b1bc4dfb5d911e86769ff1c 100644
--- a/third_party/WebKit/Source/core/html/HTMLDialogElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLDialogElement.cpp
@@ -34,6 +34,7 @@
 #include "core/frame/LocalFrameView.h"
 #include "core/frame/UseCounter.h"
 #include "core/html/HTMLFormControlElement.h"
+#include "core/html/HTMLFrameOwnerElement.h"
 #include "core/style/ComputedStyle.h"
 
 namespace blink {
@@ -82,6 +83,13 @@ static void SetFocusForDialog(HTMLDialogElement* dialog) {
 }
 
 static void InertSubtreesChanged(Document& document) {
+  if (document.GetFrame()) {
+    // SetIsInert recurses through subframes to propagate the inert bit as
+    // needed.
+    document.GetFrame()->SetIsInert(document.LocalOwner() &&

[alexmos, 2017/06/16 02:17:58]

How does this work when showModal is called in a main frame where owner is null?
 Won't we incorrectly pass the bit as false then, and set is_inert_ as false on
the main LocalFrame?  (Looks like the remote frames would still propagate the
right value, as they consult is_inert_ ||
ToHTMLFrameOwnerElement(child->Owner())->IsInert() and the latter would be
true.)

[kenrb, 2017/06/19 19:26:23]

For the main frame, is_inert_ is correctly always false, since that strictly
represents whether the owner element is inert in a parent frame. I have added a
comment to Frame.h to make that meaning clearer.

[alexmos, 2017/06/20 18:46:10]

Ah, I see - I missed this distinction that this means that the frame's owner is
inert in the parent.

+                                    document.LocalOwner()->IsInert());
+  }
+
   // When a modal dialog opens or closes, nodes all over the accessibility
   // tree can change inertness which means they must be added or removed from
   // the tree. The most foolproof way is to clear the entire tree and rebuild
@@ -189,7 +197,7 @@ void HTMLDialogElement::showModal(ExceptionState& exception_state) {
 void HTMLDialogElement::RemovedFrom(ContainerNode* insertion_point) {
   HTMLElement::RemovedFrom(insertion_point);
   SetNotCentered();
-  // FIXME: We should call inertSubtreesChanged() here.
+  InertSubtreesChanged(GetDocument());
 }
 
 void HTMLDialogElement::SetCentered(LayoutUnit centered_position) {