MacViews/a11y: Allow accessibility clients to update the selected text.

ui/accessibility/platform/ax_platform_node_mac.mm

Index: ui/accessibility/platform/ax_platform_node_mac.mm
diff --git a/ui/accessibility/platform/ax_platform_node_mac.mm b/ui/accessibility/platform/ax_platform_node_mac.mm
index be9eb9e3679d2214a2f36a34f17e09f50335b97b..9c0bf7ad0327deb3535895df506fe8899d214b69 100644
--- a/ui/accessibility/platform/ax_platform_node_mac.mm
+++ b/ui/accessibility/platform/ax_platform_node_mac.mm
@@ -378,11 +378,9 @@ void NotifyMacEvent(AXPlatformNodeCocoa* target, ui::AXEvent event_type) {
     return NO;
   }
 
-  if ([attributeName isEqualToString:NSAccessibilityValueAttribute])
+  if ([attributeName isEqualToString:NSAccessibilityValueAttribute] ||
+      [attributeName isEqualToString:NSAccessibilitySelectedTextAttribute])
     return node_->GetDelegate()->CanSetStringValue();
-  // TODO(patricialor): Implement and merge with conditional for value above.
-  if ([attributeName isEqualToString:NSAccessibilitySelectedTextAttribute])
-    return NO;
 
   if ([attributeName isEqualToString:NSAccessibilityFocusedAttribute]) {
     if (ui::AXViewState::IsFlagSet(node_->GetData().state,
@@ -398,7 +396,11 @@ void NotifyMacEvent(AXPlatformNodeCocoa* target, ui::AXEvent event_type) {
 - (void)accessibilitySetValue:(id)value forAttribute:(NSString*)attribute {
   if ([attribute isEqualToString:NSAccessibilityValueAttribute] &&
       [value isKindOfClass:[NSString class]])

[tapted, 2016/10/20 05:54:59]

perhaps at the top of the function, 

if (![value isKindOfClass:[NSString class]])
  return;

[Patti Lor, 2016/10/24 04:31:48]

This doesn't work for all attributes - e.g., NSAccessibilityFocusAttribute is
normally writable, but will be passed as a NSNumber which wraps a bool value.

[tapted, 2016/10/24 06:11:57]

Acknowledged.

-    node_->GetDelegate()->SetStringValue(base::SysNSStringToUTF16(value));
+    node_->GetDelegate()->SetStringValue(base::SysNSStringToUTF16(value),
+                                         false);

[tapted, 2016/10/20 05:54:59]

now that the body spans 2 lines, the `if` (and else) needs curlies

[Patti Lor, 2016/10/24 04:31:48]

Done.

+  else if ([attribute isEqualToString:NSAccessibilitySelectedTextAttribute] &&
+           [value isKindOfClass:[NSString class]])
+    node_->GetDelegate()->SetStringValue(base::SysNSStringToUTF16(value), true);
 
   // TODO(patricialor): Plumb through all the other writable attributes as
   // specified in accessibilityIsAttributeSettable.