Add CastContentWindow::SetCanGoBackQuery

This allows querying the CanGoBack status of the underlying app

Bug: b/145762033
Test: None
Change-Id: I330d7124dd7817db69f5ff41bfa58f6059971113
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2008066Reviewed-by: Luke Halliwell (slow) <halliwell@chromium.org>
Commit-Queue: Albert Chaulk <achaulk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#733446}

chromecast/browser/cast_content_window.cc

@@ -24,6 +24,9 @@ void CastContentWindow::RemoveObserver(Observer* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
+void CastContentWindow::SetCanGoBackQuery(
+    base::RepeatingCallback<bool()> can_go_back) {}
+
 mojom::MediaControlUi* CastContentWindow::media_controls() {
   return nullptr;
 }

chromecast/browser/cast_content_window.h

@@ -8,6 +8,7 @@
 #include <memory>
 #include <string>
 
+#include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
@@ -204,6 +205,10 @@ class CastContentWindow {
   // the window manager.
   virtual void SetHostContext(base::Value host_context) = 0;
 
+  // Set a callback that can be queried for if the owner can handle a "back"
+  // gesture. If not set the default is to assume that gestures are unhandled.
+  virtual void SetCanGoBackQuery(base::RepeatingCallback<bool()> can_go_back);
+
   // Notify the window that its visibility type has changed. This should only
   // ever be called by the window manager.
   // TODO(seantopping): Make this private to the window manager.