a11y: Exclude children of nested keyboard accessible controls from a11y tree.

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 9edb01336f2b23b0513e8bf4e20d314dc76925e0..1cbd4f2a5d915ff1febd87106f0c53c452537883 100644
--- a/ui/accessibility/platform/ax_platform_node_mac.mm
+++ b/ui/accessibility/platform/ax_platform_node_mac.mm
@@ -230,7 +230,11 @@ void NotifyMacEvent(AXPlatformNodeCocoa* target, ui::AXEvent event_type) {
 - (NSString*)getStringAttribute:(ui::AXStringAttribute)attribute;
 @end
 
-@implementation AXPlatformNodeCocoa
+@implementation AXPlatformNodeCocoa {
+  ui::AXPlatformNodeBase* node_;  // Weak. Retains us.
+}
+
+@synthesize node = node_;
 
 // A mapping of AX roles to native roles.
 + (NSString*)nativeRoleFromAXRole:(ui::AXRole)role {
@@ -290,7 +294,8 @@ void NotifyMacEvent(AXPlatformNodeCocoa* target, ui::AXEvent event_type) {
 
 - (id)accessibilityHitTest:(NSPoint)point {
   for (AXPlatformNodeCocoa* child in [self AXChildren]) {
-    if (NSPointInRect(point, child.boundsInScreen))
+    if (![child accessibilityIsIgnored] &&
+        NSPointInRect(point, [child boundsInScreen]))
       return [child accessibilityHitTest:point];
   }
   return NSAccessibilityUnignoredAncestor(self);
@@ -626,6 +631,14 @@ AXPlatformNode* AXPlatformNode::Create(AXPlatformNodeDelegate* delegate) {
   return node;
 }
 
+// static
+AX_EXPORT AXPlatformNode* AXPlatformNode::FromNativeViewAccessible(
+    gfx::NativeViewAccessible accessible) {
+  if ([accessible isKindOfClass:[AXPlatformNodeCocoa class]])
+    return [accessible node];
+  return nullptr;
+}
+
 AXPlatformNodeMac::AXPlatformNodeMac() {
 }