Bug 1665550 - part 4: Make EventStateManager update mGestureDownFrameOwner when anonymous nodes in <input> or <textarea> are replaced r=smaug

`EventStateManager` gives up to track gesture to start a drag if mouse down
content which is stored in `mGestureDownFrameOwner` gets lost its primary frame.

When user tries to start to drag selected text in `<input>` or `<textarea>`
element, mouse down content is an anonymous node in `TextControlElement`. So,
if a reflow occurs after `mousedown` event, the anonymous `<div>` element
is replaced with new one and `EventStateManager` gives up to track it.

Therefore, this patch makes `EventStateManager` do similar things as
`nsBaseDragService`.  When `nsTextControlFrame` notifies of remove/add
the anonymous nodes, `EventStateManager` tries to keep tracking gesture with
a new anonymous node.

Differential Revision: https://phabricator.services.mozilla.com/D119488

layout/forms/nsTextControlFrame.cpp

@@ -32,6 +32,7 @@
 #include "nsILayoutHistoryState.h"
 
 #include "nsFocusManager.h"
+#include "mozilla/EventStateManager.h"
 #include "mozilla/PresShell.h"
 #include "mozilla/PresState.h"
 #include "mozilla/TextEditor.h"
@@ -166,6 +167,13 @@ void nsTextControlFrame::DestroyFrom(nsIFrame* aDestructRoot,
       }
     }
   }
+  // Otherwise, EventStateManager may track gesture to start drag with native
+  // anonymous nodes in the text control element.
+  else if (textControlElement->GetPresContext(Element::eForComposedDoc)) {
+    textControlElement->GetPresContext(Element::eForComposedDoc)
+        ->EventStateManager()
+        ->TextControlRootWillBeRemoved(*textControlElement);
+  }
 
   // If we're a subclass like nsNumberControlFrame, then it owns the root of the
   // anonymous subtree where mRootNode is.
@@ -1350,6 +1358,20 @@ nsTextControlFrame::EditorInitializer::Run() {
       }
     }
   }
+  // Otherwise, EventStateManager may be tracking gesture to start a drag.
+  else if (TextControlElement* textControlElement =
+               TextControlElement::FromNode(mFrame->GetContent())) {
+    if (nsPresContext* presContext =
+            textControlElement->GetPresContext(Element::eForComposedDoc)) {
+      if (TextEditor* textEditor =
+              textControlElement->GetTextEditorWithoutCreation()) {
+        if (Element* anonymousDivElement = textEditor->GetRoot()) {
+          presContext->EventStateManager()->TextControlRootAdded(
+              *anonymousDivElement, *textControlElement);
+        }
+      }
+    }
+  }
 
   mFrame->FinishedInitializer();
   return NS_OK;