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 ddac72c464489ca43eae958db51302214a3eb90f..57163fca24a2d994efd32fe6727362f8e8a1601a 100644
--- a/chrome/browser/ui/panels/panel_browser_window.cc
+++ b/chrome/browser/ui/panels/panel_browser_window.cc
@@ -154,17 +154,9 @@ 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(