MacViews a11y: Allow accessibility clients to set the AXValue on some controls.

ui/views/accessibility/native_view_accessibility.cc

Index: ui/views/accessibility/native_view_accessibility.cc
diff --git a/ui/views/accessibility/native_view_accessibility.cc b/ui/views/accessibility/native_view_accessibility.cc
index c10e55cc3ac51e5c358cbc316bf3af411bed9d00..3231b4a587d7bae66922e165c7cccdf9ba67188a 100644
--- a/ui/views/accessibility/native_view_accessibility.cc
+++ b/ui/views/accessibility/native_view_accessibility.cc
@@ -215,6 +215,12 @@ bool NativeViewAccessibility::SetStringValue(const base::string16& new_value) {
   return true;
 }
 
+bool NativeViewAccessibility::CanSetStringValue() {

[tapted, 2016/08/11 04:23:25]

Can/should this be enforced by ui::AX_STATE_READ_ONLY? (i.e. _in theory_ the
ui::AX_STATE_READ_ONLY flag should be set for all cases *unless* there is a
set_value_callback available to change it, but in reality that might be hard

[Patti Lor, 2016/08/12 01:57:42]

I think that's a good idea - AXViewState is meant to be as much like a struct as
possible, so it doesn't enforce this. I've moved the READ_ONLY checks to here
from accessibilityIsAttributeSettable since this class is cross-platform.

+  ui::AXViewState state;
+  view_->GetAccessibleState(&state);
+  return !state.set_value_callback.is_null();
+}
+
 void NativeViewAccessibility::OnWidgetDestroying(Widget* widget) {
   if (parent_widget_ == widget) {
     parent_widget_->RemoveObserver(this);