diff --git a/gfx/tests/crashtests/crashtests.list b/gfx/tests/crashtests/crashtests.list
index e4a9be4debcc..b5594ed46c12 100644
--- a/gfx/tests/crashtests/crashtests.list
+++ b/gfx/tests/crashtests/crashtests.list
@@ -86,10 +86,10 @@ load 580100-1.html
 load 580212-1.html
 load 580233-1.html
 load 580719-1.html
-load 593526.html
-load 593526.xul
+pref(layout.css.moz-appearance.enabled,true) load 593526.html
+pref(layout.css.moz-appearance.enabled,true) load 593526.xul
 load 594654-1.xhtml
-load 595042-1.html
+pref(layout.css.moz-appearance.enabled,true) load 595042-1.html
 load 595727-1.html
 load 624198.xhtml
 load 633322-1.html
diff --git a/layout/base/crashtests/crashtests.list b/layout/base/crashtests/crashtests.list
index ea28af72d572..70f136698582 100644
--- a/layout/base/crashtests/crashtests.list
+++ b/layout/base/crashtests/crashtests.list
@@ -431,7 +431,7 @@ load 812665.html
 load 813372-1.html
 load 817219.html
 load 818454.html
-load 822865.html
+pref(layout.css.moz-appearance.enabled,true) load 822865.html
 load 824300.html
 load 824862.html
 load 826163.html
diff --git a/layout/forms/crashtests/crashtests.list b/layout/forms/crashtests/crashtests.list
index b8fe122233b3..092f0747a0ff 100644
--- a/layout/forms/crashtests/crashtests.list
+++ b/layout/forms/crashtests/crashtests.list
@@ -26,7 +26,7 @@ load 378369.html
 load 378413-1.xhtml
 load 380116-1.xhtml
 load 382212-1.xhtml
-load 382610-1.html
+pref(layout.css.moz-appearance.enabled,true) load 382610-1.html
 load 383887-1.html
 load 386554-1.html
 load 388374-1.xhtml
@@ -62,7 +62,7 @@ load 959311.html
 load 960277-2.html
 load 997709-1.html
 load 1102791.html
-skip-if(stylo) load 1140216.html # bug 1323693, bug 1341973
+pref(layout.css.moz-appearance.enabled,true) skip-if(stylo) load 1140216.html # bug 1323693, bug 1341973
 load 1182414.html
 load 1212688.html
 load 1228670.xhtml
diff --git a/layout/generic/crashtests/crashtests.list b/layout/generic/crashtests/crashtests.list
index ee272202c948..c1b7a79754a0 100644
--- a/layout/generic/crashtests/crashtests.list
+++ b/layout/generic/crashtests/crashtests.list
@@ -110,7 +110,7 @@ load 379917-1.xhtml
 load 380012-1.html
 load 381152-1.html
 load 381786-1.html
-load 382129-1.xhtml
+pref(layout.css.moz-appearance.enabled,true) load 382129-1.xhtml
 load 382131-1.html
 load 382199-1.html
 load 382208-1.xhtml
@@ -119,7 +119,7 @@ load 382396-1.xhtml
 load 382745-1.xhtml
 load 383089-1.html
 load 385265-1.xhtml
-load 385295-1.xhtml
+pref(layout.css.moz-appearance.enabled,true) load 385295-1.xhtml
 load 385344-1.html
 load 385344-2.html
 load 385414-1.html
@@ -185,7 +185,7 @@ load 400078-1.html
 load 400190.html
 load 400223-1.html # bug 1323652
 load 400232-1.html
-load 400244-1.html
+pref(layout.css.moz-appearance.enabled,true) load 400244-1.html
 load 400768-1.xhtml
 load 400768-2.xhtml
 load 401042-1.xhtml
@@ -490,9 +490,9 @@ load 762764-1.html
 load 762902.html
 load 765409.html
 asserts(0-200) load 765621.html # bug 703550
-asserts(0-200) load 767765.html # bug 407550, bug 871758, and various nscoord_MAX related asserts
+pref(layout.css.moz-appearance.enabled,true) asserts(0-200) load 767765.html # bug 407550, bug 871758, and various nscoord_MAX related asserts
 load 769120.html
-asserts(0-2) load 769303-1.html # bug 1123979
+pref(layout.css.moz-appearance.enabled,true) asserts(0-2) load 769303-1.html # bug 1123979
 load 769303-2.html
 load 777838.html
 load 783228.html
diff --git a/layout/reftests/flexbox/reftest.list b/layout/reftests/flexbox/reftest.list
index d305a7fb4b57..b4de536dcb7e 100644
--- a/layout/reftests/flexbox/reftest.list
+++ b/layout/reftests/flexbox/reftest.list
@@ -13,7 +13,7 @@
 include pagination/reftest.list
 
 # Tests for cross-axis alignment (align-self / align-items properties)
-fails == flexbox-align-self-baseline-horiz-2.xhtml  flexbox-align-self-baseline-horiz-2-ref.xhtml # bug 793456, and possibly others
+pref(layout.css.moz-appearance.enabled,true) fails == flexbox-align-self-baseline-horiz-2.xhtml  flexbox-align-self-baseline-horiz-2-ref.xhtml # bug 793456, and possibly others
 # This one fails on windows R (but not Ru, strangely) and GTK.
 # On Windows R and GTK, the single-line <label> flex item has a different
 # background size in test vs. ref
diff --git a/layout/reftests/forms/input/color/reftest.list b/layout/reftests/forms/input/color/reftest.list
index 148cb4bad971..ce000d61e1ec 100644
--- a/layout/reftests/forms/input/color/reftest.list
+++ b/layout/reftests/forms/input/color/reftest.list
@@ -10,5 +10,5 @@ fails-if(Android) == margin-padding-1.html margin-padding-1-ref.html
 == block-invalidate-1.html block-invalidate-1-ref.html
 == block-invalidate-2.html block-invalidate-2-ref.html
 fuzzy-if(gtkWidget,8,33) fuzzy-if(skiaContent,8,35) fails-if(Android) == transformations-1.html transformations-1-ref.html
-fails-if(Android) == custom-style-1.html custom-style-1-ref.html
+pref(layout.css.moz-appearance.enabled,true) fails-if(Android) == custom-style-1.html custom-style-1-ref.html
 fails-if(Android) == custom-style-2.html custom-style-2-ref.html
diff --git a/layout/reftests/forms/input/number/reftest.list b/layout/reftests/forms/input/number/reftest.list
index fae23b900a5d..d947cb99012e 100644
--- a/layout/reftests/forms/input/number/reftest.list
+++ b/layout/reftests/forms/input/number/reftest.list
@@ -27,10 +27,10 @@ fuzzy-if(skiaContent,2,13) == show-value.html show-value-ref.html
 == number-auto-width-1.html number-auto-width-1-ref.html
 
 # min-height/max-height tests:
-skip-if(Android) == number-min-height-1.html number-min-height-1-ref.html
-skip-if(Android) == number-min-height-2.html number-min-height-2-ref.html
-skip-if(Android) == number-max-height-1.html number-max-height-1-ref.html
-skip-if(Android) == number-max-height-2.html number-max-height-2-ref.html
+pref(layout.css.moz-appearance.enabled,true) skip-if(Android) == number-min-height-1.html number-min-height-1-ref.html
+pref(layout.css.moz-appearance.enabled,true) skip-if(Android) == number-min-height-2.html number-min-height-2-ref.html
+pref(layout.css.moz-appearance.enabled,true) skip-if(Android) == number-max-height-1.html number-max-height-1-ref.html
+pref(layout.css.moz-appearance.enabled,true) skip-if(Android) == number-max-height-2.html number-max-height-2-ref.html
 
 # number of significant fractional digits:
 == number-significant-fractional-digits.html number-significant-fractional-digits-ref.html
@@ -54,4 +54,4 @@ fuzzy(128,4) == number-reframe-anon-text-field.html number-reframe-anon-text-fie
 == pseudo-classes.html about:blank
 
 # Style inheritance:
-== number-style-inheritance.html number-style-inheritance-ref.html
+pref(layout.css.moz-appearance.enabled,true) == number-style-inheritance.html number-style-inheritance-ref.html
diff --git a/layout/reftests/forms/progress/reftest.list b/layout/reftests/forms/progress/reftest.list
index 445a76a4d9d2..4606d482e9e7 100644
--- a/layout/reftests/forms/progress/reftest.list
+++ b/layout/reftests/forms/progress/reftest.list
@@ -1,3 +1,6 @@
+# This enables '-moz-appearance' for author sheets:
+default-preferences pref(layout.css.moz-appearance.enabled,true)
+
 == values.html values-ref.html
 == values-rtl.html values-rtl-ref.html
 == margin-padding.html margin-padding-ref.html
diff --git a/layout/reftests/forms/textbox/reftest.list b/layout/reftests/forms/textbox/reftest.list
index eb0b8fc9d5eb..56ee22751f38 100644
--- a/layout/reftests/forms/textbox/reftest.list
+++ b/layout/reftests/forms/textbox/reftest.list
@@ -8,4 +8,4 @@ skip-if(cocoaWidget||Android) != accesskey-3.xul accesskey-3-notref.xul
 skip-if(cocoaWidget||Android) == accesskey-4.xul accesskey-4-ref.xul
 skip-if(cocoaWidget||Android) != accesskey-4.xul accesskey-4-notref.xul
 skip-if(Android) == align-baseline-1.xul align-baseline-1-ref.xul # test for bug 494901
-skip-if(Android) == setsize.xul setsize-ref.xul
+pref(layout.css.moz-appearance.enabled,true) skip-if(Android) == setsize.xul setsize-ref.xul
diff --git a/layout/reftests/native-theme/reftest.list b/layout/reftests/native-theme/reftest.list
index c2df3caaa6b5..62aa99e29ad8 100644
--- a/layout/reftests/native-theme/reftest.list
+++ b/layout/reftests/native-theme/reftest.list
@@ -30,11 +30,11 @@ fails-if(!nativeThemePref) != checkbox-native.html checkbox-nonnative.html
 != 427122-1.html 427122-1-ref.html
 
 # 403458 is a Windows-only bug
-skip-if(!winWidget) != 403458-winmenu-ltr.xul 403458-winmenu-rtl.xul
+pref(layout.css.moz-appearance.enabled,true) skip-if(!winWidget) != 403458-winmenu-ltr.xul 403458-winmenu-rtl.xul
 
 == 470711-1.xul 470711-1-ref.xul
 
-== 482955-1.xul 482955-1-ref.xul
+pref(layout.css.moz-appearance.enabled,true) == 482955-1.xul 482955-1-ref.xul
 
 == 492155-1.html about:blank
 == 492155-2.html about:blank
@@ -78,7 +78,7 @@ skip-if(!winWidget) == scroll-thumb-minimum-size-notheme.html scroll-thumb-minim
 # animated progress bars.
 # Nothing shows up on Android, presumably because that appearance type is
 # not implemented.
-skip-if(cocoaWidget) skip-if(winWidget) == progress-overflow.html progress-overflow-ref.html
-fails-if(Android) skip-if(cocoaWidget) skip-if(winWidget) != progress-overflow-small.html progress-nobar.html
+pref(layout.css.moz-appearance.enabled,true) skip-if(cocoaWidget) skip-if(winWidget) == progress-overflow.html progress-overflow-ref.html
+pref(layout.css.moz-appearance.enabled,true) fails-if(Android) skip-if(cocoaWidget) skip-if(winWidget) != progress-overflow-small.html progress-nobar.html
 
 == 676387-1.xul 676387-1-ref.xul
diff --git a/layout/reftests/svg/reftest.list b/layout/reftests/svg/reftest.list
index 95ac1a4ec023..cfb3a2e0424c 100644
--- a/layout/reftests/svg/reftest.list
+++ b/layout/reftests/svg/reftest.list
@@ -214,7 +214,7 @@ fuzzy-if(skiaContent,1,800000) == filters-and-group-opacity-01.svg filters-and-g
 == foreignObject-ancestor-style-change-01.svg foreignObject-ancestor-style-change-01-ref.svg
 == foreignObject-change-transform-01.svg pass.svg
 == foreignObject-display-01.svg pass.svg
-== foreignObject-form-theme.svg foreignObject-form-theme-ref.html
+pref(layout.css.moz-appearance.enabled,true) == foreignObject-form-theme.svg foreignObject-form-theme-ref.html
 == foreignObject-img-form-theme.html foreignObject-img-form-theme-ref.html
 == foreignObject-move-repaint-01.svg pass.svg
 == foreignObject-overflow-01.svg pass.svg
diff --git a/layout/reftests/writing-mode/reftest.list b/layout/reftests/writing-mode/reftest.list
index 006f1b0cd9dd..e05293471a31 100644
--- a/layout/reftests/writing-mode/reftest.list
+++ b/layout/reftests/writing-mode/reftest.list
@@ -69,7 +69,7 @@ fuzzy-if(Android,1,18) == ua-style-sheet-checkbox-radio-1.html ua-style-sheet-ch
 skip-if(Android) fuzzy-if(skiaContent&&!Android,2,6) == ua-style-sheet-button-1.html ua-style-sheet-button-1a-ref.html
 skip-if(!(Android)) == ua-style-sheet-button-1.html ua-style-sheet-button-1b-ref.html
 == ua-style-sheet-input-color-1.html ua-style-sheet-input-color-1-ref.html
-fuzzy-if(gtkWidget,1,15) == ua-style-sheet-input-number-1.html ua-style-sheet-input-number-1-ref.html
+pref(layout.css.moz-appearance.enabled,true) fuzzy-if(gtkWidget,1,15) == ua-style-sheet-input-number-1.html ua-style-sheet-input-number-1-ref.html
 
 HTTP(..) == 1127488-align-default-horizontal-tb-ltr.html 1127488-align-top-left-ref.html
 HTTP(..) == 1127488-align-start-horizontal-tb-ltr.html 1127488-align-top-left-ref.html
diff --git a/layout/reftests/writing-mode/ua-style-sheet-input-number-1-ref.html b/layout/reftests/writing-mode/ua-style-sheet-input-number-1-ref.html
index c270fc188d6a..c2a8e31e7048 100644
--- a/layout/reftests/writing-mode/ua-style-sheet-input-number-1-ref.html
+++ b/layout/reftests/writing-mode/ua-style-sheet-input-number-1-ref.html
@@ -6,7 +6,7 @@
 .ltr, .rtl, .v-rl { border: 1px solid blue; }
 div { padding: 10px; }
 .a { -moz-appearance:textfield; }
-.b { -moz-appearance:none; appearance: none; }
+.b { -moz-appearance:none; }
 
 .ltr input[type="number"],
 .rtl input[type="number"] {
diff --git a/layout/reftests/writing-mode/ua-style-sheet-input-number-1.html b/layout/reftests/writing-mode/ua-style-sheet-input-number-1.html
index facb5b3ca1e3..b46b24426783 100644
--- a/layout/reftests/writing-mode/ua-style-sheet-input-number-1.html
+++ b/layout/reftests/writing-mode/ua-style-sheet-input-number-1.html
@@ -6,7 +6,7 @@
 .ltr, .rtl, .v-rl { border: 1px solid blue; }
 div { padding: 10px; }
 .a { -moz-appearance:textfield; }
-.b { -moz-appearance:none; appearance: none; }
+.b { -moz-appearance:none; }
 </style>
 <div class=ltr>
   <input type=number value=123><br><br>
diff --git a/layout/svg/crashtests/crashtests.list b/layout/svg/crashtests/crashtests.list
index 1ae767ec7537..cc6dfbcc1925 100644
--- a/layout/svg/crashtests/crashtests.list
+++ b/layout/svg/crashtests/crashtests.list
@@ -74,7 +74,7 @@ load 420697-2.svg
 load 429774-1.svg
 load 441368-1.svg
 load 453754-1.svg
-load 455314-1.xhtml
+pref(layout.css.moz-appearance.enabled,true) load 455314-1.xhtml
 load 458453.html
 load 459666-1.html # bug 1323652
 load 459883.xhtml
@@ -153,7 +153,7 @@ load 789390-1.html # bug 1323652
 load 790072.svg
 load 791826-1.svg
 load 808318-1.svg
-load 803562-1.svg
+pref(layout.css.moz-appearance.enabled,true) load 803562-1.svg
 load 813420-1.svg
 load 841163-1.svg
 load 841812-1.svg
diff --git a/layout/xul/reftest/reftest.list b/layout/xul/reftest/reftest.list
index 39f35357747c..60aa2ee57ffd 100644
--- a/layout/xul/reftest/reftest.list
+++ b/layout/xul/reftest/reftest.list
@@ -1,5 +1,5 @@
-fails-if(Android) == textbox-multiline-noresize.xul textbox-multiline-ref.xul # reference is blank on Android (due to no native theme support?)
-!= textbox-multiline-resize.xul textbox-multiline-ref.xul
+pref(layout.css.moz-appearance.enabled,true) fails-if(Android) == textbox-multiline-noresize.xul textbox-multiline-ref.xul # reference is blank on Android (due to no native theme support?)
+pref(layout.css.moz-appearance.enabled,true) != textbox-multiline-resize.xul textbox-multiline-ref.xul
 == popup-explicit-size.xul popup-explicit-size-ref.xul
 random-if(Android) == image-size.xul image-size-ref.xul
 == image-scaling-min-height-1.xul image-scaling-min-height-1-ref.xul
diff --git a/toolkit/content/tests/reftests/reftest.list b/toolkit/content/tests/reftests/reftest.list
index b59bd946ea07..9e0fd0bbcc64 100644
--- a/toolkit/content/tests/reftests/reftest.list
+++ b/toolkit/content/tests/reftests/reftest.list
@@ -1,3 +1,3 @@
-random-if(cocoaWidget) == bug-442419-progressmeter-max.xul bug-442419-progressmeter-max-ref.xul # fails most of the time on Mac because progress meter animates
+pref(layout.css.moz-appearance.enabled,true) random-if(cocoaWidget) == bug-442419-progressmeter-max.xul bug-442419-progressmeter-max-ref.xul # fails most of the time on Mac because progress meter animates
 != textbox-multiline-default-value.xul textbox-multiline-empty.xul
 == videocontrols-dynamically-add-cc.html videocontrols-dynamically-add-cc-ref.html
diff --git a/toolkit/themes/osx/reftests/reftest.list b/toolkit/themes/osx/reftests/reftest.list
index 27034dd8629c..3307aae3764f 100644
--- a/toolkit/themes/osx/reftests/reftest.list
+++ b/toolkit/themes/osx/reftests/reftest.list
@@ -1,5 +1,5 @@
-skip-if(!cocoaWidget) == 482681.xul 482681-ref.xul
-skip-if(!cocoaWidget) == radiosize.xul radiosize-ref.xul
-skip-if(!cocoaWidget) == checkboxsize.xul checkboxsize-ref.xul
+pref(layout.css.moz-appearance.enabled,true) skip-if(!cocoaWidget) == 482681.xul 482681-ref.xul
+pref(layout.css.moz-appearance.enabled,true) skip-if(!cocoaWidget) == radiosize.xul radiosize-ref.xul
+pref(layout.css.moz-appearance.enabled,true) skip-if(!cocoaWidget) == checkboxsize.xul checkboxsize-ref.xul
 skip-if(!cocoaWidget) == baseline.xul about:blank
 skip-if(!cocoaWidget) == nostretch.xul nostretch-ref.xul
diff --git a/view/crashtests/crashtests.list b/view/crashtests/crashtests.list
index 2156501ce0d2..97c7b1cae6e4 100644
--- a/view/crashtests/crashtests.list
+++ b/view/crashtests/crashtests.list
@@ -2,7 +2,7 @@ load 38589-1.xul
 load 64049-1.html
 load 281743-1.html
 load 323497-1.html
-load 382756-1.xul
+pref(layout.css.moz-appearance.enabled,true) load 382756-1.xul
 load 387745-1.svg
 load 399852.html
 load 429315-1.html
diff --git a/widget/cocoa/crashtests/crashtests.list b/widget/cocoa/crashtests/crashtests.list
index b65fe0139402..2335fc3016dc 100644
--- a/widget/cocoa/crashtests/crashtests.list
+++ b/widget/cocoa/crashtests/crashtests.list
@@ -1,11 +1,11 @@
 skip-if(!cocoaWidget) load 373122-1.html # bug 1300017
 load 397209-1.html
 load 403296-1.xhtml
-load 419737-1.html
-load 435223-1.html
+pref(layout.css.moz-appearance.enabled,true) load 419737-1.html
+pref(layout.css.moz-appearance.enabled,true) load 435223-1.html
 load 444260-1.xul
 load 444864-1.html
 load 449111-1.html
-load 460349-1.xhtml
-load 460387-1.html
+pref(layout.css.moz-appearance.enabled,true) load 460349-1.xhtml
+pref(layout.css.moz-appearance.enabled,true) load 460387-1.html
 load 464589-1.html
diff --git a/widget/crashtests/crashtests.list b/widget/crashtests/crashtests.list
index 957f3f005cea..a8565a9124ac 100644
--- a/widget/crashtests/crashtests.list
+++ b/widget/crashtests/crashtests.list
@@ -1,4 +1,4 @@
 load 303901-1.html
 load 303901-2.html
-load 380359-1.xhtml
+pref(layout.css.moz-appearance.enabled,true) load 380359-1.xhtml
 load 1128214.html
diff --git a/widget/gtk/crashtests/crashtests.list b/widget/gtk/crashtests/crashtests.list
index 9ae47c2233c1..acd9bf4b5f02 100644
--- a/widget/gtk/crashtests/crashtests.list
+++ b/widget/gtk/crashtests/crashtests.list
@@ -1,2 +1,2 @@
-load 540078-1.xhtml
+pref(layout.css.moz-appearance.enabled,true) load 540078-1.xhtml
 load 673390-1.html
diff --git a/widget/reftests/reftest.list b/widget/reftests/reftest.list
index 26057327b843..69603e498ccf 100644
--- a/widget/reftests/reftest.list
+++ b/widget/reftests/reftest.list
@@ -1,6 +1,6 @@
-skip-if(!cocoaWidget) != 507947.html about:blank
-== progressbar-fallback-default-style.html progressbar-fallback-default-style-ref.html
+pref(layout.css.moz-appearance.enabled,true) skip-if(!cocoaWidget) != 507947.html about:blank
+pref(layout.css.moz-appearance.enabled,true) == progressbar-fallback-default-style.html progressbar-fallback-default-style-ref.html
 fuzzy-if(Android,17,1120) == meter-native-style.html meter-native-style-ref.html
 skip-if(!cocoaWidget) == meter-vertical-native-style.html meter-vertical-native-style-ref.html # dithering
-== meter-fallback-default-style.html meter-fallback-default-style-ref.html
-load 664925.xhtml
+pref(layout.css.moz-appearance.enabled,true) == meter-fallback-default-style.html meter-fallback-default-style-ref.html
+pref(layout.css.moz-appearance.enabled,true) load 664925.xhtml