[Cast MRP] Workaround for DCHECK failure when attempting to cast.

CastDialogSinkButton::RequestFocus is called recursively, resulting
in a DCHECK failure.  As a workaround, this function now detects
when it is called recursively and aborts prematurely.

Change-Id: I4847f862868ef9c15ed0ca6cd54cb36cc559a901
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1488581
Commit-Queue: John Williams <jrw@chromium.org>
Reviewed-by: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660949}

chrome/browser/ui/views/media_router/cast_dialog_sink_button.cc

@@ -4,6 +4,9 @@
 
 #include "chrome/browser/ui/views/media_router/cast_dialog_sink_button.h"
 
+#include <memory>
+
+#include "base/debug/stack_trace.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/app/vector_icons/vector_icons.h"
 #include "chrome/browser/ui/views/chrome_layout_provider.h"
@@ -12,6 +15,7 @@
 #include "chrome/common/media_router/issue.h"
 #include "chrome/grit/generated_resources.h"
 #include "components/vector_icons/vector_icons.h"
+#include "content/public/browser/browser_thread.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/gfx/color_palette.h"
@@ -198,6 +202,15 @@ void CastDialogSinkButton::OnEnabledChanged() {
 }
 
 void CastDialogSinkButton::RequestFocus() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  static bool requesting_focus = false;
+  if (requesting_focus) {
+    // TODO(jrw): Figure out why this happens.
+    DLOG(ERROR) << "Recursive call to RequestFocus\n"
+                << base::debug::StackTrace();
+    return;
+  }
+  requesting_focus = true;
   if (GetEnabled()) {
     HoverButton::RequestFocus();
   } else {
@@ -205,6 +218,7 @@ void CastDialogSinkButton::RequestFocus() {
     // want focus.
     icon_view()->RequestFocus();
   }
+  requesting_focus = false;
 }
 
 void CastDialogSinkButton::OnFocus() {