Bug 1600536 - user-select: auto on input / textarea should behave as text. r=mats

This is covered by existing tests, via the removal of the rule in forms.css

Differential Revision: https://phabricator.services.mozilla.com/D56355

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

layout/generic/nsFrame.cpp

@@ -4464,9 +4464,10 @@ static StyleUserSelect UsedUserSelect(const nsIFrame* aFrame) {
     return style;
   }
 
-  if (IsEditingHost(aFrame)) {
+  if (aFrame->IsTextInputFrame() || IsEditingHost(aFrame)) {
     // We don't implement 'contain' itself, but we make 'text' behave as
-    // 'contain' for contenteditable elements anyway so this is ok.
+    // 'contain' for contenteditable and <input> / <textarea> elements anyway so
+    // this is ok.
     return StyleUserSelect::Text;
   }
 

layout/style/res/forms.css

@@ -99,7 +99,6 @@ input {
   font: -moz-field;
   text-rendering: optimizeLegibility;
   cursor: text;
-  user-select: text;
   overflow-clip-box: padding-box content-box;
 }
 
@@ -125,7 +124,6 @@ textarea {
   vertical-align: text-bottom;
   cursor: text;
   resize: both;
-  user-select: text;
   white-space: pre-wrap;
   word-wrap: break-word;
   overflow-clip-box: content-box;