Removed dead code from chrome/browser/extensions/api/web_navigation

chrome/browser/extensions/api/web_navigation/frame_navigation_state.cc

Index: chrome/browser/extensions/api/web_navigation/frame_navigation_state.cc
diff --git a/chrome/browser/extensions/api/web_navigation/frame_navigation_state.cc b/chrome/browser/extensions/api/web_navigation/frame_navigation_state.cc
index fbd9ac1bb147df149c5241fdb3adb1c02e1aaf9e..05df57ddd888d8639a0ed599292e2de9138301f6 100644
--- a/chrome/browser/extensions/api/web_navigation/frame_navigation_state.cc
+++ b/chrome/browser/extensions/api/web_navigation/frame_navigation_state.cc
@@ -37,10 +37,6 @@ FrameNavigationState::FrameID::FrameID(
       render_view_host(render_view_host) {
 }
 
-bool FrameNavigationState::FrameID::IsValid() const {
-  return frame_num >= 0 && render_view_host;
-}
-
 bool FrameNavigationState::FrameID::operator<(
     const FrameNavigationState::FrameID& other) const {
   return frame_num < other.frame_num ||