Expose the MacViewsWebUIDialogs feature flag to chrome://flags

chrome/browser/ui/browser_dialogs.h

Index: chrome/browser/ui/browser_dialogs.h
diff --git a/chrome/browser/ui/browser_dialogs.h b/chrome/browser/ui/browser_dialogs.h
index 38be04392d6c6819e13c55bfd367be45819d3ff3..af24d621584b39b7d0424c8e4f949857f5ffbfd4 100644
--- a/chrome/browser/ui/browser_dialogs.h
+++ b/chrome/browser/ui/browser_dialogs.h
@@ -18,6 +18,10 @@ class GURL;
 class LoginHandler;
 class Profile;
 
+namespace base {
+struct Feature;
+}
+
 namespace bookmarks {
 class BookmarkBubbleObserver;
 }
@@ -48,6 +52,11 @@ class WebDialogDelegate;
 
 namespace chrome {
 
+#if defined(OS_MACOSX)
+// Makes ToolkitViewsWebUIDialogsEnabled() available to chrome://flags.
+extern const base::Feature kMacViewsWebUIDialogs;
+#endif  // OS_MACOSX
+
 // Shows or hides the Task Manager. |browser| can be NULL when called from Ash.
 // Returns a pointer to the underlying TableModel, which can be ignored, or used
 // for testing.
@@ -89,8 +98,7 @@ content::ColorChooser* ShowColorChooser(content::WebContents* web_contents,
 bool ToolkitViewsDialogsEnabled();
 
 // For Mac, returns true if Chrome should show an equivalent toolkit-views based
-// dialog instead of a WebUI-styled Cocoa dialog. ToolkitViewsDialogsEnabled()
-// implies ToolkitViewsWebUIDialogsEnabled().
+// dialog instead of a WebUI-styled Cocoa dialog.
 bool ToolkitViewsWebUIDialogsEnabled();
 
 // Shows a Views website settings bubble at the given anchor point.