Add UIAccessibilityTraitUpdatesFrequently to progressBar role

Summary:
Changelog:
Add UIAccessibilityTraitUpdatesFrequently when the AccessibilityRole is set to progressBar. This trait tells the accessibility system where content may change with every percentage point, but without annoying the user with constant announcements.

Reviewed By: ikenwoo

Differential Revision: D30510587

fbshipit-source-id: e75690a2a56ce42476dc999383cf58c0811fcbdf

React/Views/RCTViewManager.m

@@ -51,7 +51,7 @@ @implementation RCTConvert (UIAccessibilityTraits)
       @"menu" : @(UIAccessibilityTraitNone),
       @"menubar" : @(UIAccessibilityTraitNone),
       @"menuitem" : @(UIAccessibilityTraitNone),
-      @"progressbar" : @(UIAccessibilityTraitNone),
+      @"progressbar" : @(UIAccessibilityTraitUpdatesFrequently),
       @"radio" : @(UIAccessibilityTraitNone),
       @"radiogroup" : @(UIAccessibilityTraitNone),
       @"scrollbar" : @(UIAccessibilityTraitNone),
@@ -172,7 +172,8 @@ - (RCTShadowView *)shadowView
   const UIAccessibilityTraits AccessibilityRolesMask = UIAccessibilityTraitNone | UIAccessibilityTraitButton |
       UIAccessibilityTraitLink | UIAccessibilityTraitSearchField | UIAccessibilityTraitImage |
       UIAccessibilityTraitKeyboardKey | UIAccessibilityTraitStaticText | UIAccessibilityTraitAdjustable |
-      UIAccessibilityTraitHeader | UIAccessibilityTraitSummaryElement | SwitchAccessibilityTrait;
+      UIAccessibilityTraitHeader | UIAccessibilityTraitSummaryElement | UIAccessibilityTraitTabBar |
+      UIAccessibilityTraitUpdatesFrequently | SwitchAccessibilityTrait;
   view.reactAccessibilityElement.accessibilityTraits =
       view.reactAccessibilityElement.accessibilityTraits & ~AccessibilityRolesMask;
   UIAccessibilityTraits newTraits = json ? [RCTConvert UIAccessibilityTraits:json] : defaultView.accessibilityTraits;

ReactCommon/react/renderer/components/view/accessibilityPropsConversions.h

@@ -98,6 +98,10 @@ inline void fromString(const std::string &string, AccessibilityTraits &result) {
     result = AccessibilityTraits::TabBar;
     return;
   }
+  if (string == "progressbar") {
+    result = AccessibilityTraits::UpdatesFrequently;
+    return;
+  }
   result = AccessibilityTraits::None;
 }