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 88ab503003939c38fe2445d8d7efe90d2dd0a465..cacc3c48def623326221a89fb99f7b2e704204e7 100644
--- a/ui/accessibility/platform/ax_platform_node_mac.mm
+++ b/ui/accessibility/platform/ax_platform_node_mac.mm
@@ -365,11 +365,9 @@ void NotifyMacEvent(NSView* 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,
@@ -386,6 +384,9 @@ void NotifyMacEvent(NSView* target, ui::AXEvent event_type) {
   if ([attribute isEqualToString:NSAccessibilityValueAttribute] &&
       [value isKindOfClass:[NSString class]])
     node_->GetDelegate()->SetStringValue(base::SysNSStringToUTF16(value));
+  if ([attribute isEqualToString:NSAccessibilitySelectedTextAttribute] &&

[tapted, 2016/09/27 07:16:30]

else if (or alter to support the `bool` replace arg as required

[Patti Lor, 2016/10/20 04:19:34]

Done.

+      [value isKindOfClass:[NSString class]])
+    node_->GetDelegate()->ReplaceSelectedText(base::SysNSStringToUTF16(value));
 
   // TODO(patricialor): Plumb through all the other writable attributes as
   // specified in accessibilityIsAttributeSettable.