Refactor browser window zoom handling and enable zoom icon on all platforms.

chrome/browser/ui/panels/panel_browser_window.cc

Index: chrome/browser/ui/panels/panel_browser_window.cc
diff --git a/chrome/browser/ui/panels/panel_browser_window.cc b/chrome/browser/ui/panels/panel_browser_window.cc
index 7f1f84beb4357472721af65ceaef907d2066cb6b..b7e3b5317da27cdac6c04c4d9f51a55ad394569b 100644
--- a/chrome/browser/ui/panels/panel_browser_window.cc
+++ b/chrome/browser/ui/panels/panel_browser_window.cc
@@ -158,17 +158,9 @@ void PanelBrowserWindow::SetStarredState(bool is_starred) {
   // have starred state.
 }
 
-void PanelBrowserWindow::SetZoomIconState(ZoomController::ZoomIconState state) {
-  // Since panels don't have an Omnibox, they don't have a zoom icon.
-}
-
-void PanelBrowserWindow::SetZoomIconTooltipPercent(int zoom_percent) {
-  // Since panels don't have an Omnibox, they don't have a zoom icon.
-}
-
-void PanelBrowserWindow::ShowZoomBubble(int zoom_percent) {
+void PanelBrowserWindow::ZoomChangedForActiveTab(bool can_show_bubble) {
   // Since panels don't have an Omnibox, they don't have a zoom icon, so no
-  // bubble will appear from it.
+  // view icon nor bubble will appear for this action.
 }
 
 void PanelBrowserWindow::EnterFullscreen(