Add new CanZoom/Zoom API (fixes #3284)

Add a simpler CanZoom/Zoom API as an alternative to the more error-prone
SetZoomLevel/GetZoomLevel API. Both APIs are now implemented for both runtimes.
With the Chrome runtime a zoom notification bubble will be displayed unless
CefBrowserSettings.chrome_zoom_bubble is set to STATE_DISABLED.

To test:
- Run cefclient and select zoom entries from the Tests menu.
- chrome: Run cefclient with `--hide-chrome-bubbles` command-line flag to hide
  the zoom notification bubble.

libcef/browser/alloy/alloy_browser_host_impl.cc

@@ -34,10 +34,10 @@
 #include "base/functional/callback_helpers.h"
 #include "chrome/browser/file_select_helper.h"
 #include "chrome/browser/picture_in_picture/picture_in_picture_window_manager.h"
+#include "components/zoom/page_zoom.h"
 #include "content/browser/gpu/compositor_util.h"
 #include "content/public/browser/desktop_media_id.h"
 #include "content/public/browser/file_select_listener.h"
-#include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/keyboard_event_processing_result.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/navigation_handle.h"
@@ -330,31 +330,6 @@ CefWindowHandle AlloyBrowserHostImpl::GetOpenerWindowHandle() {
   return opener_;
 }
 
-double AlloyBrowserHostImpl::GetZoomLevel() {
-  // Verify that this method is being called on the UI thread.
-  if (!CEF_CURRENTLY_ON_UIT()) {
-    DCHECK(false) << "called on invalid thread";
-    return 0;
-  }
-
-  if (web_contents()) {
-    return content::HostZoomMap::GetZoomLevel(web_contents());
-  }
-
-  return 0;
-}
-
-void AlloyBrowserHostImpl::SetZoomLevel(double zoomLevel) {
-  if (CEF_CURRENTLY_ON_UIT()) {
-    if (web_contents()) {
-      content::HostZoomMap::SetZoomLevel(web_contents(), zoomLevel);
-    }
-  } else {
-    CEF_POST_TASK(CEF_UIT, base::BindOnce(&AlloyBrowserHostImpl::SetZoomLevel,
-                                          this, zoomLevel));
-  }
-}
-
 void AlloyBrowserHostImpl::Find(const CefString& searchText,
                                 bool forward,
                                 bool matchCase,
@@ -1118,6 +1093,11 @@ bool AlloyBrowserHostImpl::DidAddMessageToConsole(
                                                     line_no, source_id);
 }
 
+void AlloyBrowserHostImpl::ContentsZoomChange(bool zoom_in) {
+  zoom::PageZoom::Zoom(
+      web_contents(), zoom_in ? content::PAGE_ZOOM_IN : content::PAGE_ZOOM_OUT);
+}
+
 void AlloyBrowserHostImpl::BeforeUnloadFired(content::WebContents* source,
                                              bool proceed,
                                              bool* proceed_to_fire_unload) {