fix: undo and redo broken in webviews (#22911)

When propagating the undo and redo events from the menu, Chromium was not
properly sending the events to the focused WebContents. This fixes that by ensuring that the events are sent to the proper WebContents.

patches/chromium/.patches

@@ -93,3 +93,4 @@ gpu_notify_when_dxdiag_request_fails.patch
 feat_allow_embedders_to_add_observers_on_created_hunspell.patch
 feat_add_onclose_to_messageport.patch
 gin_allow_passing_an_objecttemplate_to_objecttemplatebuilder.patch
+fix_undo_redo_broken_in_webviews.patch

patches/chromium/fix_undo_redo_broken_in_webviews.patch

@@ -0,0 +1,36 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Shelley Vohr <[email protected]>
+Date: Tue, 31 Mar 2020 14:32:33 -0700
+Subject: fix: undo redo broken in webviews
+
+When propagating the undo and redo events from the menu, Chromium was not
+properly sending the events to the focused webcontents on macOS. This fixes
+that error. A crbug has been opened at https://bugs.chromium.org/p/chromium/issues/detail?id=1067284
+and this patch will be removed when it has been resolved upstream.
+
+diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
+index 591305cb57a2f89067b25189b9c33d92858f01a0..a3112cb03bc73eb670631ff429f38414537f19cf 100644
+--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
++++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
+@@ -38,6 +38,7 @@
+ #include "content/browser/renderer_host/render_widget_host_input_event_router.h"
+ #import "content/browser/renderer_host/text_input_client_mac.h"
+ #import "content/browser/renderer_host/ui_events_helper.h"
++#include "content/browser/web_contents/web_contents_impl.h"
+ #include "content/common/text_input_state.h"
+ #include "content/common/view_messages.h"
+ #include "content/public/browser/browser_context.h"
+@@ -978,7 +979,12 @@ void CombineTextNodesAndMakeCallback(SpeechCallback callback,
+ }
+ 
+ WebContents* RenderWidgetHostViewMac::GetWebContents() {
+-  return WebContents::FromRenderViewHost(RenderViewHost::From(host()));
++  auto* wc = WebContents::FromRenderViewHost(RenderViewHost::From(host()));
++  if (wc) {
++    WebContentsImpl* web_contents_impl = static_cast<WebContentsImpl*>(wc);
++    return web_contents_impl->GetFocusedWebContents();
++  }
++  return wc;
+ }
+ 
+ bool RenderWidgetHostViewMac::GetCachedFirstRectForCharacterRange(