Bug 1642261 - Part 2: Add telemetry for -moz-appearance usage. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D77637

dom/base/UseCounters.conf

@@ -12,7 +12,7 @@
 //
 //   (b) a comment, which is a line that begins with "//"
 //
-//   (c) one of four possible use counter declarations:
+//   (c) one of three possible use counter declarations:
 //
 //         method <IDL interface name>.<IDL operation name>
 //         attribute <IDL interface name>.<IDL attribute name>
@@ -26,6 +26,7 @@
 // To actually cause use counters to be incremented, DOM methods
 // and attributes must have a [UseCounter] extended attribute in
 // the Web IDL file.
+//
 // Custom counters are incremented when
 // SetUseCounter(eUseCounter_custom_MyName) is called on a Document object.
 //
@@ -342,3 +343,61 @@ method Window.webkitSpeechRecognitionEvent
 method Window.webkitStorageInfo
 method Window.Worklet
 method Window.WritableStream
+
+// -moz-appearance property usage
+custom Appearance_Widget_Button sets -moz-appearance to button on an element that normally has some other non-none appearance
+custom Appearance_Widget_Textfield sets -moz-appearance to textfield on an element that normally has some other non-none appearance
+custom Appearance_Widget_MenulistButton sets -moz-appearance to menulist-button on an element that normally has some other non-none appearance
+custom Appearance_Widget_Searchfield sets -moz-appearance to searchfield on an element that normally has some other non-none appearance
+custom Appearance_Widget_Textarea sets -moz-appearance to textarea on an element that normally has some other non-none appearance
+custom Appearance_Widget_Checkbox sets -moz-appearance to checkbox on an element that normally has some other non-none appearance
+custom Appearance_Widget_Radio sets -moz-appearance to radio on an element that normally has some other non-none appearance
+custom Appearance_Widget_Menulist sets -moz-appearance to menulist on an element that normally has some other non-none appearance
+custom Appearance_Widget_Listbox sets -moz-appearance to listbox on an element that normally has some other non-none appearance
+custom Appearance_Widget_Meter sets -moz-appearance to meter on an element that normally has some other non-none appearance
+custom Appearance_Widget_ProgressBar sets -moz-appearance to progress-bar on an element that normally has some other non-none appearance
+custom Appearance_Widget_NumberInput sets -moz-appearance to number-input on an element that normally has some other non-none appearance
+custom Appearance_Widget_Range sets -moz-appearance to range on an element that normally has some other non-none appearance
+custom Appearance_Widget_InnerSpinButton sets -moz-appearance to inner-spin-button on an element that normally has some other non-none appearance
+custom Appearance_Widget_ProgressbarVertical sets -moz-appearance to progressbar-vertical on an element that normally has some other non-none appearance
+custom Appearance_Widget_ScaleHorizontal sets -moz-appearance to scale-horizontal on an element that normally has some other non-none appearance
+custom Appearance_Widget_ScaleVertical sets -moz-appearance to scale-vertical on an element that normally has some other non-none appearance
+custom Appearance_Widget_ScalethumbHorizontal sets -moz-appearance to scalethumb-horizontal on an element that normally has some other non-none appearance
+custom Appearance_Widget_ScalethumbVertical sets -moz-appearance to scalethumb-vertical on an element that normally has some other non-none appearance
+custom Appearance_Widget_Scalethumbstart sets -moz-appearance to scalethumbstart on an element that normally has some other non-none appearance
+custom Appearance_Widget_Scalethumbend sets -moz-appearance to scalethumbend on an element that normally has some other non-none appearance
+custom Appearance_Widget_Scalethumbtick sets -moz-appearance to scalethumbtick on an element that normally has some other non-none appearance
+custom Appearance_Widget_RangeThumb sets -moz-appearance to range-thumb on an element that normally has some other non-none appearance
+custom Appearance_Widget_ScrollbarthumbHorizontal sets -moz-appearance to scrollbarthumb-horizontal on an element that normally has some other non-none appearance
+custom Appearance_Widget_ScrollbarthumbVertical sets -moz-appearance to scrollbarthumb-vertical on an element that normally has some other non-none appearance
+custom Appearance_Widget_ScrollbartrackHorizontal sets -moz-appearance to scrollbartrack-horizontal on an element that normally has some other non-none appearance
+custom Appearance_Widget_ScrollbartrackVertical sets -moz-appearance to scrollbartrack-vertical on an element that normally has some other non-none appearance
+custom Appearance_NonWidget_Button sets -moz-appearance to button on an element that normally has appearance none
+custom Appearance_NonWidget_Textfield sets -moz-appearance to textfield on an element that normally has appearance none
+custom Appearance_NonWidget_MenulistButton sets -moz-appearance to menulist-button on an element that normally has appearance none
+custom Appearance_NonWidget_Searchfield sets -moz-appearance to searchfield on an element that normally has appearance none
+custom Appearance_NonWidget_Textarea sets -moz-appearance to textarea on an element that normally has appearance none
+custom Appearance_NonWidget_Checkbox sets -moz-appearance to checkbox on an element that normally has appearance none
+custom Appearance_NonWidget_Radio sets -moz-appearance to radio on an element that normally has appearance none
+custom Appearance_NonWidget_Menulist sets -moz-appearance to menulist on an element that normally has appearance none
+custom Appearance_NonWidget_Listbox sets -moz-appearance to listbox on an element that normally has appearance none
+custom Appearance_NonWidget_Meter sets -moz-appearance to meter on an element that normally has appearance none
+custom Appearance_NonWidget_ProgressBar sets -moz-appearance to progress-bar on an element that normally has appearance none
+custom Appearance_NonWidget_NumberInput sets -moz-appearance to number-input on an element that normally has appearance none
+custom Appearance_NonWidget_Range sets -moz-appearance to range on an element that normally has appearance none
+custom Appearance_NonWidget_InnerSpinButton sets -moz-appearance to inner-spin-button on an element that normally has appearance none
+custom Appearance_NonWidget_ProgressbarVertical sets -moz-appearance to progressbar-vertical on an element that normally has appearance none
+custom Appearance_NonWidget_ScaleHorizontal sets -moz-appearance to scale-horizontal on an element that normally has appearance none
+custom Appearance_NonWidget_ScaleVertical sets -moz-appearance to scale-vertical on an element that normally has appearance none
+custom Appearance_NonWidget_ScalethumbHorizontal sets -moz-appearance to scalethumb-horizontal on an element that normally has appearance none
+custom Appearance_NonWidget_ScalethumbVertical sets -moz-appearance to scalethumb-vertical on an element that normally has appearance none
+custom Appearance_NonWidget_Scalethumbstart sets -moz-appearance to scalethumbstart on an element that normally has appearance none
+custom Appearance_NonWidget_Scalethumbend sets -moz-appearance to scalethumbend on an element that normally has appearance none
+custom Appearance_NonWidget_Scalethumbtick sets -moz-appearance to scalethumbtick on an element that normally has appearance none
+custom Appearance_NonWidget_RangeThumb sets -moz-appearance to range-thumb on an element that normally has appearance none
+custom Appearance_NonWidget_ScrollbarthumbHorizontal sets -moz-appearance to scrollbarthumb-horizontal on an element that normally has appearance none
+custom Appearance_NonWidget_ScrollbarthumbVertical sets -moz-appearance to scrollbarthumb-vertical on an element that normally has appearance none
+custom Appearance_NonWidget_ScrollbartrackHorizontal sets -moz-appearance to scrollbartrack-horizontal on an element that normally has appearance none
+custom Appearance_NonWidget_ScrollbartrackVertical sets -moz-appearance to scrollbartrack-vertical on an element that normally has appearance none
+custom Appearance_Overridden_NumberInput used `-moz-appearance: number-input` to override some other value on an <input type=number>
+custom Appearance_Overridden_Range used `-moz-appearance: range` to override some other value on an <input type=range>

dom/base/test/browser.ini

@@ -23,6 +23,7 @@ support-files =
   file_bug1303838_with_iframe.html
   file_messagemanager_unload.html
   file_pluginAudio.html
+  file_use_counter_appearance.html
   file_use_counter_outer.html
   file_use_counter_style.html
   file_use_counter_svg_getElementById.svg

dom/base/test/browser_use_counters.js

@@ -81,6 +81,38 @@ add_task(async function() {
     "CSS_PROPERTY_WebkitPaddingStart"
   );
 
+  // Check for -moz-appearance related use counters.
+  const appearanceCounters = [
+    ["APPEARANCE_WIDGET_BUTTON", 0],
+    ["APPEARANCE_NONWIDGET_BUTTON", 0],
+    ["APPEARANCE_WIDGET_TEXTFIELD", 0],
+    ["APPEARANCE_NONWIDGET_TEXTFIELD", 0],
+    ["APPEARANCE_WIDGET_RADIO", 0],
+    ["APPEARANCE_NONWIDGET_RADIO", 0],
+    ["APPEARANCE_WIDGET_CHECKBOX", 1],
+    ["APPEARANCE_NONWIDGET_CHECKBOX", 0],
+    ["APPEARANCE_WIDGET_MENULISTBUTTON", 0],
+    ["APPEARANCE_NONWIDGET_MENULISTBUTTON", 1],
+    ["APPEARANCE_WIDGET_METER", 0],
+    ["APPEARANCE_NONWIDGET_METER", 0],
+    ["APPEARANCE_WIDGET_TEXTAREA", 0],
+    ["APPEARANCE_NONWIDGET_TEXTAREA", 0],
+    ["APPEARANCE_WIDGET_RANGE", 0],
+    ["APPEARANCE_NONWIDGET_RANGE", 0],
+    ["APPEARANCE_OVERRIDDEN_RANGE", 1],
+    ["APPEARANCE_WIDGET_NUMBERINPUT", 0],
+    ["APPEARANCE_NONWIDGET_NUMBERINPUT", 0],
+    ["APPEARANCE_OVERRIDDEN_NUMBERINPUT", 0],
+  ];
+  for (let [name, value] of appearanceCounters) {
+    await check_use_counter_iframe(
+      "file_use_counter_appearance.html",
+      name,
+      /* check_documents = */ true,
+      value
+    );
+  }
+
   // Check that even loads from the imglib cache update use counters.  The
   // images should still be there, because we just loaded them in the last
   // set of tests.  But we won't get updated counts for the document
@@ -183,9 +215,12 @@ function grabHistogramsFromContent(use_counter_middlefix, page_before = null) {
 var check_use_counter_iframe = async function(
   file,
   use_counter_middlefix,
-  check_documents = true
+  check_documents = true,
+  value = 1
 ) {
-  info("checking " + file + " with histogram " + use_counter_middlefix);
+  info(
+    `checking ${file} with histogram ${use_counter_middlefix} and expected value ${value}`
+  );
 
   let newTab = BrowserTestUtils.addTab(gBrowser, "about:blank");
   gBrowser.selectedTab = newTab;
@@ -240,17 +275,17 @@ var check_use_counter_iframe = async function(
 
   is(
     histogram_page_after,
-    histogram_page_before + 1,
+    histogram_page_before + value,
     "page counts for " + use_counter_middlefix + " after are correct"
   );
   ok(
-    histogram_toplevel_docs_after >= histogram_toplevel_docs_before + 1,
+    histogram_toplevel_docs_after >= histogram_toplevel_docs_before + value,
     "top level document counts are correct"
   );
   if (check_documents) {
     is(
       histogram_document_after,
-      histogram_document_before + 1,
+      histogram_document_before + value,
       "document counts for " + use_counter_middlefix + " after are correct"
     );
   }

dom/base/test/file_use_counter_appearance.html

@@ -0,0 +1,30 @@
+<!DOCTYPE html>
+
+<!-- a value set by the UA sheet -->
+<button>a button</button>
+
+<!-- a value set on a widget that normally has that appearance -->
+<input style="-moz-appearance: textfield;">
+
+<!-- a value set on a widget that doesn't normally have that appearance -->
+<input type="radio" style="-moz-appearance: checkbox;">
+
+<!-- a value set on a non-widget -->
+<div style="-moz-appearance: menulist-button;"></div>
+
+<!-- a standard value set on a widget that normally has that appearance, cascading over some other value -->
+<style>
+textarea { -moz-appearance: meter; }
+textarea { -moz-appearance: textarea; }
+</style>
+<textarea></textarea>
+
+<!-- a non-standard value set on a widget that normally has that appearance, cascading over some other value -->
+<style>
+input[type=range] { -moz-appearance: none; }
+input[type=range] { -moz-appearance: range; }
+</style>
+<input type="range">
+
+<!-- a non-standard value set by UA sheets, which we want to track for cascading over some other value -->
+<input type="number">

layout/generic/nsFrame.cpp

@@ -1410,11 +1410,123 @@ void nsIFrame::DidSetComputedStyle(ComputedStyle* aOldComputedStyle) {
     }
   }
 
+  RecordAppearanceTelemetry();
+
   RemoveStateBits(NS_FRAME_SIMPLE_EVENT_REGIONS | NS_FRAME_SIMPLE_DISPLAYLIST);
 
   mMayHaveRoundedCorners = true;
 }
 
+void nsIFrame::RecordAppearanceTelemetry() {
+  // Record uses of -moz-appearance values in the wild that would affect our
+  // ability to implement the css-ui-4 unprefixed appearance property.
+
+  StyleAppearance appearance = StyleDisplay()->mAppearance;
+  StyleAppearance defaultAppearance = StyleDisplay()->mDefaultAppearance;
+
+  if ((appearance == StyleAppearance::None &&
+       defaultAppearance == StyleAppearance::None) ||
+      !mContent || mContent->IsInNativeAnonymousSubtree()) {
+    return;
+  }
+
+  // The css-ui-4 specification defines unprefixed appearance as taking values:
+  //
+  //   none | auto | button | textfield | menulist-button | <compat-auto>
+  //
+  // where:
+  //
+  //   <compat-auto> = searchfield | textarea | push-button |
+  //                   slider-horizontal | checkbox | radio | square-button |
+  //                   menulist | listbox | meter | progress-bar
+  //
+  // Of these, we don't currently support auto, push-button, slider-horizontal,
+  // or square-button.  The auto value we will support soon, but the other three
+  // may not be required for compatibility.  So we don't record any telemetry
+  // for the use of those values.
+  //
+  // We support a number of values exposed to content, which are not in the
+  // spec:
+  //
+  //   number-input | range | inner-spin-button | progressbar-vertical |
+  //   scale-horizontal | scale-vertical | scalethumb-horizontal |
+  //   scalethumb-vertical | scalethumbstart | scalethumbend | scalethumbtick |
+  //   range-thumb | scrollbarthumb-horizontal | scrollbarthumb-vertical |
+  //   scrollbartrack-horizontal | scrollbartrack-vertical
+  //
+  // Of these, number-input and range are used by UA sheets (set on <input
+  // type=number> and <input type=range> elements) and exposed to content.  We
+  // want to measure whether these values are being used to override some other
+  // values (e.g. none) in author sheets on these elements, since that means we
+  // should add them to the <compat-auto> set.
+  if (appearance == defaultAppearance) {
+    UseCounter counter = eUseCounter_UNKNOWN;
+    switch (appearance) {
+      case StyleAppearance::NumberInput:
+        counter = eUseCounter_custom_Appearance_Overridden_NumberInput;
+        break;
+      case StyleAppearance::Range:
+        counter = eUseCounter_custom_Appearance_Overridden_Range;
+        break;
+      default:
+        return;
+    }
+    if (mComputedStyle->HasOverriddenAppearance(appearance)) {
+      PresContext()->Document()->SetUseCounter(counter);
+    }
+    return;
+  }
+
+  // For all values, we want to check whether they have been set on an element
+  // that would not normally have that value from the UA sheets.  We record
+  // separate use counters for whether the -moz-appearance value was used with
+  // an underlying value of none ("on a non-widget") or with some non-none value
+  // ("on a widget").
+  UseCounter onWidget;
+  UseCounter onNonWidget;
+#define CASE(name_)                                                \
+  case StyleAppearance::name_:                                     \
+    onWidget = eUseCounter_custom_Appearance_Widget_##name_;       \
+    onNonWidget = eUseCounter_custom_Appearance_NonWidget_##name_; \
+    break;
+  switch (appearance) {
+    CASE(Button)
+    CASE(Textfield)
+    CASE(MenulistButton)
+    CASE(Searchfield)
+    CASE(Textarea)
+    CASE(Checkbox)
+    CASE(Radio)
+    CASE(Menulist)
+    CASE(Listbox)
+    CASE(Meter)
+    CASE(ProgressBar)
+    CASE(NumberInput)
+    CASE(Range)
+    CASE(InnerSpinButton)
+    CASE(ProgressbarVertical)
+    CASE(ScaleHorizontal)
+    CASE(ScaleVertical)
+    CASE(ScalethumbHorizontal)
+    CASE(ScalethumbVertical)
+    CASE(Scalethumbstart)
+    CASE(Scalethumbend)
+    CASE(Scalethumbtick)
+    CASE(RangeThumb)
+    CASE(ScrollbarthumbHorizontal)
+    CASE(ScrollbarthumbVertical)
+    CASE(ScrollbartrackHorizontal)
+    CASE(ScrollbartrackVertical)
+    default:
+      return;
+  }
+#undef CASE
+
+  auto counter =
+      defaultAppearance == StyleAppearance::None ? onNonWidget : onWidget;
+  PresContext()->Document()->SetUseCounter(counter);
+}
+
 #ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
 void nsIFrame::AssertNewStyleIsSane(ComputedStyle& aNewStyle) {
   MOZ_DIAGNOSTIC_ASSERT(

layout/generic/nsIFrame.h

@@ -799,6 +799,9 @@ class nsIFrame : public nsQueryFrame {
   // Use PeekStyleData instead.
   virtual void DidSetComputedStyle(ComputedStyle* aOldComputedStyle);
 
+ private:
+  void RecordAppearanceTelemetry();
+
  public:
 /**
  * Define typesafe getter functions for each style struct by

layout/style/ComputedStyle.cpp

@@ -411,4 +411,8 @@ bool ComputedStyle::EqualForCachedAnonymousContentStyle(
 
 #endif
 
+bool ComputedStyle::HasOverriddenAppearance(StyleAppearance aAppearance) const {
+  return Servo_ComputedValues_HasOverriddenAppearance(this, aAppearance);
+}
+
 }  // namespace mozilla

layout/style/ComputedStyle.h

@@ -297,6 +297,8 @@ class ComputedStyle {
 
   StyleWritingMode WritingMode() const { return {mSource.WritingMode().mBits}; }
 
+  bool HasOverriddenAppearance(StyleAppearance) const;
+
  protected:
   // Needs to be friend so that it can call the destructor without making it
   // public.

layout/style/nsStyleStruct.cpp

@@ -2229,6 +2229,7 @@ nsStyleDisplay::nsStyleDisplay(const Document& aDocument)
       mOriginalDisplay(StyleDisplay::Inline),
       mContain(StyleContain::NONE),
       mAppearance(StyleAppearance::None),
+      mDefaultAppearance(StyleAppearance::None),
       mPosition(StylePositionProperty::Static),
       mFloat(StyleFloat::None),
       mBreakType(StyleClear::None),
@@ -2298,6 +2299,7 @@ nsStyleDisplay::nsStyleDisplay(const nsStyleDisplay& aSource)
       mOriginalDisplay(aSource.mOriginalDisplay),
       mContain(aSource.mContain),
       mAppearance(aSource.mAppearance),
+      mDefaultAppearance(aSource.mDefaultAppearance),
       mPosition(aSource.mPosition),
       mFloat(aSource.mFloat),
       mBreakType(aSource.mBreakType),
@@ -2471,6 +2473,10 @@ nsChangeHint nsStyleDisplay::CalcDifference(
     hint |= nsChangeHint_NeutralChange;
   }
 
+  if (mDefaultAppearance != aNewData.mDefaultAppearance) {
+    hint |= nsChangeHint_NeutralChange;
+  }
+
   if (mOverflowX != aNewData.mOverflowX || mOverflowY != aNewData.mOverflowY) {
     const bool isScrollable = IsScrollableOverflow();
     if (isScrollable != aNewData.IsScrollableOverflow()) {

layout/style/nsStyleStruct.h

@@ -1216,6 +1216,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleDisplay {
                                            //         mDisplay
   mozilla::StyleContain mContain;
   mozilla::StyleAppearance mAppearance;
+  mozilla::StyleAppearance mDefaultAppearance;
   mozilla::StylePositionProperty mPosition;
 
   mozilla::StyleFloat mFloat;

layout/style/res/forms.css

@@ -85,6 +85,7 @@ label {
 input {
   display: inline-block;
   -moz-appearance: textfield;
+  -moz-default-appearance: textfield;
   /* The sum of border and padding on block-start and block-end
      must be the same here, for buttons, and for <select> (including its
      internal padding magic) */
@@ -107,6 +108,7 @@ input::placeholder {
 
 textarea {
   -moz-appearance: textarea;
+  -moz-default-appearance: textarea;
   margin-block: 1px;
   border: 2px inset ThreeDLightShadow;
   /* The 1px inline padding is for parity with Win/IE */
@@ -225,6 +227,7 @@ select {
   box-sizing: border-box;
   user-select: none;
   -moz-appearance: menulist;
+  -moz-default-appearance: menulist;
   border-width: 2px;
   border-style: inset;
   overflow: -moz-hidden-unscrollable;
@@ -253,6 +256,7 @@ select:is([size], [multiple], [size][multiple]) {
   padding-inline: 0;
   vertical-align: text-bottom;
   -moz-appearance: listbox;
+  -moz-default-appearance: listbox;
 }
 
 select:is([size="0"], [size="1"]) {
@@ -262,6 +266,7 @@ select:is([size="0"], [size="1"]) {
   vertical-align: baseline;
   padding: unset;
   -moz-appearance: menulist;
+  -moz-default-appearance: menulist;
 }
 
 select > button {
@@ -439,6 +444,7 @@ optgroup:disabled {
 /* hidden inputs */
 input[type="hidden"] {
   -moz-appearance: none;
+  -moz-default-appearance: none;
   display: none !important;
   padding: unset;
   border: 0;
@@ -449,6 +455,7 @@ input[type="hidden"] {
 /* image buttons */
 input[type="image"] {
   -moz-appearance: none;
+  -moz-default-appearance: none;
   padding: unset;
   border: none;
   background-color: transparent;
@@ -476,6 +483,7 @@ input[type="image"]:disabled {
 /* radio buttons */
 input[type="radio"] {
   -moz-appearance: radio;
+  -moz-default-appearance: radio;
   margin-block: 3px 0;
   margin-inline: 5px 3px;
 }
@@ -483,6 +491,7 @@ input[type="radio"] {
 /* check boxes */
 input[type="checkbox"] {
   -moz-appearance: checkbox;
+  -moz-default-appearance: checkbox;
   margin-block: 3px;
   margin-inline: 4px 3px;
 }
@@ -529,6 +538,7 @@ button,
 ::file-chooser-button,
 input:is([type="color"], [type="reset"], [type="button"], [type="submit"]) {
   -moz-appearance: button;
+  -moz-default-appearance: button;
   /* The sum of border and padding on block-start and block-end
      must be the same here, for text inputs, and for <select>.
      Note -moz-focus-inner padding does not affect button size. */
@@ -673,6 +683,7 @@ input[type="file"] {
 
   /* Revert rules which apply on all inputs. */
   -moz-appearance: none;
+  -moz-default-appearance: none;
   cursor: default;
 
   border: none;
@@ -756,6 +767,7 @@ output:-moz-ui-invalid {
 
 progress {
   -moz-appearance: progress-bar;
+  -moz-default-appearance: progress-bar;
   display: inline-block;
   vertical-align: -0.2em;
 
@@ -785,6 +797,7 @@ progress {
 
 meter {
   -moz-appearance: meter;
+  -moz-default-appearance: meter;
   display: inline-block;
   vertical-align: -0.2em;
   background: linear-gradient(#e6e6e6, #e6e6e6, #eeeeee 20%, #cccccc 45%, #cccccc 55%);
@@ -817,6 +830,7 @@ meter {
 
 input[type=range] {
   -moz-appearance: range;
+  -moz-default-appearance: range;
   margin: 2px;
   /* Override some rules that apply on all input types: */
   cursor: default;
@@ -887,6 +901,7 @@ input[type=range]::-moz-range-thumb {
    * to get rid of it. The thumb's -moz-appearance is fixed.
    */
   -moz-appearance: range-thumb !important;
+  -moz-default-appearance: range-thumb: !important;
   /* Prevent styling that would change the type of frame we construct. */
   display: block !important;
   float: none !important;
@@ -905,6 +920,7 @@ input[type=range]::-moz-range-thumb {
 
 input[type="number"] {
   -moz-appearance: number-input;
+  -moz-default-appearance: number-input;
 }
 
 input[type=number]::-moz-number-wrapper {

layout/style/res/geckoview.css

@@ -12,6 +12,7 @@ button,
 xul|button,
 * > input:not(:-moz-any([type="image"], [type="checkbox"], [type="radio"])) {
   -moz-appearance: none !important;  /* See bug 598421 for fixing the platform */
+  -moz-default-appearance: none !important;
 }
 
 textarea,

layout/style/test/test_non_content_accessible_properties.html

@@ -22,6 +22,7 @@ const NON_CONTENT_ACCESSIBLE_PROPERTIES = [
   "-moz-font-smoothing-background-color",
   "-moz-min-font-size-ratio",
   "-moz-script-size-multiplier",
+  "-moz-default-appearance",
   // TODO(emilio): Whenever we stop using `-moz-binding` in a gazillion tests
   // we should add it here.
 ];

layout/svg/svg.css

@@ -54,6 +54,7 @@ svg:not(:root), symbol, image, marker, pattern, foreignObject {
 
 foreignObject {
   -moz-appearance: none ! important;
+  -moz-default-appearance: none ! important;
   margin: 0 ! important;
   padding: 0 ! important;
   border-width: 0 ! important;
@@ -63,6 +64,7 @@ foreignObject {
 @media all and (-moz-is-resource-document) {
  foreignObject *|* {
    -moz-appearance: none !important;
+   -moz-default-appearance: none !important;
  }
 }
 

servo/components/style/properties/declaration_block.rs

@@ -340,6 +340,21 @@ impl PropertyDeclarationBlock {
             .find(|(declaration, _)| declaration.id() == property)
     }
 
+    /// Get a declaration for a given property with the specified importance.
+    #[inline]
+    pub fn get_at_importance(
+        &self,
+        property: PropertyDeclarationId,
+        importance: Importance,
+    ) -> Option<&PropertyDeclaration> {
+        let (declaration, i) = self.get(property)?;
+        if i == importance {
+            Some(declaration)
+        } else {
+            None
+        }
+    }
+
     /// Tries to serialize a given shorthand from the declarations in this
     /// block.
     pub fn shorthand_to_css(

servo/components/style/properties/longhands/box.mako.rs

@@ -638,6 +638,21 @@ ${helpers.predefined_type(
     gecko_ffi_name="mAppearance",
 )}
 
+// A UA-sheet only property that is always set to the same value as
+// -moz-appearance.  Used to record telemetry for when author sheets
+// override the value of -moz-appearance; see
+// nsIFrame::RecordAppearanceTelemetry.
+${helpers.predefined_type(
+    "-moz-default-appearance",
+    "Appearance",
+    "computed::Appearance::None",
+    engines="gecko",
+    animation_value_type="none",
+    spec="Internal (not web-exposed)",
+    enabled_in="ua",
+    gecko_ffi_name="mDefaultAppearance",
+)}
+
 ${helpers.single_keyword(
     "-moz-orient",
     "inline block horizontal vertical",

servo/components/style/properties/properties.mako.rs

@@ -2111,7 +2111,8 @@ impl PropertyId {
 pub struct WideKeywordDeclaration {
     #[css(skip)]
     id: LonghandId,
-    keyword: CSSWideKeyword,
+    /// The CSS-wide keyword.
+    pub keyword: CSSWideKeyword,
 }
 
 /// An unparsed declaration that contains `var()` functions.

servo/ports/geckolib/glue.rs

@@ -3983,6 +3983,41 @@ pub extern "C" fn Servo_ComputedValues_EqualForCachedAnonymousContentStyle(
     differing_properties.is_empty()
 }
 
+#[no_mangle]
+pub extern "C" fn Servo_ComputedValues_HasOverriddenAppearance(
+    cv: &ComputedValues,
+    appearance: specified::Appearance,
+) -> bool {
+    use style::properties::{CSSWideKeyword, PropertyDeclaration};
+
+    let rules = match cv.rules {
+        Some(ref rules) => rules,
+        None => return false,
+    };
+
+    let global_style_data = &*GLOBAL_STYLE_DATA;
+    let guard = global_style_data.shared_lock.read();
+
+    let id = PropertyDeclarationId::Longhand(LonghandId::MozAppearance);
+
+    // Look for any -moz-appearance declarations on rules at the Author level
+    // which set some non-default value.  revert would cause us to revert to
+    // the default value, so don't count that.  Declarations with variables
+    // could resolve to a default or non-default value depending on computed
+    // style, but should be rare enough on -moz-appearance to be OK to count
+    // as a non-default value.
+    rules
+        .self_and_ancestors()
+        .filter(|n| n.cascade_level().origin() == Origin::Author)
+        .flat_map(|n| n.style_source().unwrap().read(&guard).get_at_importance(id, n.importance()))
+        .any(|declaration| {
+            match declaration {
+                PropertyDeclaration::MozAppearance(a) => *a != appearance,
+                _ => declaration.get_css_wide_keyword() != Some(CSSWideKeyword::Revert),
+            }
+        })
+}
+
 #[no_mangle]
 pub extern "C" fn Servo_StyleSet_Init(doc: &structs::Document) -> *mut RawServoStyleSet {
     let data = Box::new(PerDocumentStyleData::new(doc));