Bug 1503656 - Part 6. Rebuild CSS environment when safe area insets a…

…re changed. r=emilio

Safe area insets can be changed dynamically (i.e. window is fullscreen and etc), so if it is updated, we have to re-parse CSS.

Differential Revision: https://phabricator.services.mozilla.com/D52512

--HG--
extra : moz-landing-system : lando

layout/base/nsPresContext.cpp

@@ -2581,7 +2581,13 @@ DynamicToolbarState nsPresContext::GetDynamicToolbarState() const {
 }
 
 void nsPresContext::SetSafeAreaInsets(const ScreenIntMargin& aSafeAreaInsets) {
+  if (mSafeAreaInsets == aSafeAreaInsets) {
+    return;
+  }
   mSafeAreaInsets = aSafeAreaInsets;
+
+  PostRebuildAllStyleDataEvent(nsChangeHint(0),
+                               RestyleHint::RecascadeSubtree());
 }
 
 #ifdef DEBUG