Bug 1829327 - Use scrollbar-width style instead of ui.scrollbarFadeBeginDelay to hide overlay scrollbars. r=botond,geckoview-reviewers,owlish

Differential Revision: https://phabricator.services.mozilla.com/D176745

mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/DynamicToolbarTest.kt

@@ -585,14 +585,6 @@ class DynamicToolbarTest : BaseSessionTest() {
     @WithDisplay(height = SCREEN_HEIGHT, width = SCREEN_WIDTH)
     @Test
     fun zoomedOverflowHidden() {
-        // Set ui.scrollbarFadeBeginDelay value to 0 to hide the overlayed scrollbars
-        // immediately.
-        sessionRule.setPrefsUntilTestEnd(
-            mapOf(
-                "ui.scrollbarFadeBeginDelay" to 0
-            )
-        )
-
         val reference = getComparisonScreenshot(SCREEN_WIDTH, SCREEN_HEIGHT)
 
         val dynamicToolbarMaxHeight = SCREEN_HEIGHT / 2
@@ -607,6 +599,9 @@ class DynamicToolbarTest : BaseSessionTest() {
         // Change the body background color to match the reference image's background color.
         mainSession.evaluateJS("document.body.style.background = 'rgb(0, 128, 0)'")
 
+        // Hide the vertical scrollbar.
+        mainSession.evaluateJS("document.documentElement.style.scrollbarWidth = 'none'")
+
         // Zoom in the content so that the content's visual viewport can be scrollable.
         mainSession.setResolutionAndScaleTo(10.0f)
 
@@ -623,14 +618,6 @@ class DynamicToolbarTest : BaseSessionTest() {
     @WithDisplay(height = SCREEN_HEIGHT, width = SCREEN_WIDTH)
     @Test
     fun zoomedPositionFixedRoot() {
-        // Set ui.scrollbarFadeBeginDelay value to 0 to hide the overlayed scrollbars
-        // immediately.
-        sessionRule.setPrefsUntilTestEnd(
-            mapOf(
-                "ui.scrollbarFadeBeginDelay" to 0
-            )
-        )
-
         val reference = getComparisonScreenshot(SCREEN_WIDTH, SCREEN_HEIGHT)
 
         val dynamicToolbarMaxHeight = SCREEN_HEIGHT / 2
@@ -650,6 +637,9 @@ class DynamicToolbarTest : BaseSessionTest() {
         mainSession.evaluateJS("document.body.style.overflow = 'scroll'")
         mainSession.evaluateJS("document.documentElement.style.position = 'fixed'")
 
+        // Hide the vertical scrollbar.
+        mainSession.evaluateJS("document.documentElement.style.scrollbarWidth = 'none'")
+
         // Zoom in the content so that the content's visual viewport can be scrollable.
         mainSession.setResolutionAndScaleTo(10.0f)
 
@@ -666,14 +656,6 @@ class DynamicToolbarTest : BaseSessionTest() {
     @WithDisplay(height = SCREEN_HEIGHT, width = SCREEN_WIDTH)
     @Test
     fun backgroundImageFixed() {
-        // Set ui.scrollbarFadeBeginDelay value to 0 to hide the overlayed scrollbars
-        // immediately.
-        sessionRule.setPrefsUntilTestEnd(
-            mapOf(
-                "ui.scrollbarFadeBeginDelay" to 0
-            )
-        )
-
         val reference = getComparisonScreenshot(SCREEN_WIDTH, SCREEN_HEIGHT)
 
         val dynamicToolbarMaxHeight = SCREEN_HEIGHT / 2
@@ -692,6 +674,9 @@ class DynamicToolbarTest : BaseSessionTest() {
         // Make the root element scrollable.
         mainSession.evaluateJS("document.documentElement.style.height = '100vh'")
 
+        // Hide the vertical scrollbar.
+        mainSession.evaluateJS("document.documentElement.style.scrollbarWidth = 'none'")
+
         mainSession.flushApzRepaints()
 
         // Simulate the dynamic toolbar being hidden by the scroll
@@ -707,14 +692,6 @@ class DynamicToolbarTest : BaseSessionTest() {
     @WithDisplay(height = SCREEN_HEIGHT, width = SCREEN_WIDTH)
     @Test
     fun backgroundAttachmentFixed() {
-        // Set ui.scrollbarFadeBeginDelay value to 0 to hide the overlayed scrollbars
-        // immediately.
-        sessionRule.setPrefsUntilTestEnd(
-            mapOf(
-                "ui.scrollbarFadeBeginDelay" to 0
-            )
-        )
-
         val reference = getComparisonScreenshot(SCREEN_WIDTH, SCREEN_HEIGHT)
 
         val dynamicToolbarMaxHeight = SCREEN_HEIGHT / 2
@@ -733,6 +710,9 @@ class DynamicToolbarTest : BaseSessionTest() {
         // Make the root element scrollable.
         mainSession.evaluateJS("document.documentElement.style.height = '100vh'")
 
+        // Hide the vertical scrollbar.
+        mainSession.evaluateJS("document.documentElement.style.scrollbarWidth = 'none'")
+
         mainSession.flushApzRepaints()
 
         // Simulate the dynamic toolbar being hidden by the scroll