MacViews: Fix accessibility hit tests, provide AXTitle

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 89444bf0c6fc94c35e48945a9e872c6ee53a89c0..f472e173aa270890d40e15151f77042623dc772c 100644
--- a/ui/accessibility/platform/ax_platform_node_mac.mm
+++ b/ui/accessibility/platform/ax_platform_node_mac.mm
@@ -244,6 +244,13 @@ RoleMap BuildSubroleMap() {
   return [NSValue valueWithSize:self.boundsInScreen.size];
 }
 
+- (NSString*)AXTitle {
+  std::string value;
+  if (node_->GetStringAttribute(ui::AX_ATTR_NAME, &value))
+    return base::SysUTF8ToNSString(value);
+  return nil;
+}
+
 // NSAccessibility informal protocol implementation.
 
 - (BOOL)accessibilityIsIgnored {
@@ -269,7 +276,12 @@ RoleMap BuildSubroleMap() {
     NSAccessibilityPositionAttribute,
     NSAccessibilityRoleAttribute,
     NSAccessibilitySizeAttribute,
+
+    // Always add title. Cocoa asks for it regardless of it appearing in here,

[dmazzoni, 2015/03/06 07:58:01]

Rather than a comment for "title", I'd maybe just put a comment at the top
saying "these attributes are required on all accessibility objects" - later
we'll add more below that are optional.

[tapted, 2015/03/06 11:01:18]

Done. Added the comment at top.

The comment on Title didn't really capture what was "weird" about what Cocoa was
doing, so I've updated it to say "Title is required for most elements. Cocoa
asks for the value even if it is omitted here, but won't present it to
accessibility APIs without this."

I think we could just add it optionally too after checking
node_->HasStringAttribute(ui::AX_ATTR_NAME) and everything would still work
fine. (And maybe that's better -- happy to change it). But it felt inconsistent
to unconditionally give an answer to AXTitle, and plenty of Apple's own UI seems
to do it this way (i.e. present the attribute name, but return <nil> if there's
nothing appropriate).

Either way, easy to move down to the optional segment when this is fleshed out
more :)

+    // most things should have it, and it's OK to return nil.
+    NSAccessibilityTitleAttribute,
   ];
+  // TODO(tapted): Add additional attributes based on role.
 }
 
 - (BOOL)accessibilityIsAttributeSettable:(NSString*)attribute {