refactor: fix modernize-return-braced-init-list warnings (#44838)

* refactor: avoid repeating the return type from the declaration; use a braced initializer list instead [modernize-return-braced-init-list]

* refactor: avoid repeating the return type from the declaration; use a braced initializer list instead [modernize-return-braced-init-list]

NB: using the braced-initializer list uncovered an error here:
the float returned by std::floor() can't be implicitly cast to
an int. This is solved by using base::ClampFloor<int>() instead.
std::floor()

shell/browser/web_contents_permission_helper.cc

@@ -53,8 +53,7 @@ namespace {
 
   // If the device id wasn't specified then this is a screen capture request
   // (i.e. chooseDesktopMedia() API wasn't used to generate device id).
-  return content::DesktopMediaID(content::DesktopMediaID::TYPE_SCREEN,
-                                 -1 /* kFullDesktopScreenId */);
+  return {content::DesktopMediaID::TYPE_SCREEN, -1 /* kFullDesktopScreenId */};
 }
 
 #if BUILDFLAG(IS_MAC)