Views a11y: Implement AXPlatformNode::FromNativeViewAccessible on all platforms.

ui/accessibility/platform/ax_platform_node.cc

Index: ui/accessibility/platform/ax_platform_node.cc
diff --git a/ui/accessibility/platform/ax_platform_node.cc b/ui/accessibility/platform/ax_platform_node.cc
index a521f84f9792419a0c8dd09041e002deaf262555..93a374abbacd9dd610e47b1aa8d1dd64803fbe17 100644
--- a/ui/accessibility/platform/ax_platform_node.cc
+++ b/ui/accessibility/platform/ax_platform_node.cc
@@ -21,17 +21,6 @@ base::LazyInstance<UniqueIdMap>::DestructorAtExit g_unique_id_map =
     LAZY_INSTANCE_INITIALIZER;
 }
 
-#if !defined(OS_WIN)
-// This is the default implementation for platforms where native views
-// accessibility is unsupported or unfinished.
-//
-// static
-AXPlatformNode* AXPlatformNode::FromNativeViewAccessible(
-    gfx::NativeViewAccessible accessible) {
-  return nullptr;
-}
-#endif
-
 AXPlatformNode::AXPlatformNode() : unique_id_(GetNextAXPlatformNodeUniqueId()) {
   g_unique_id_map.Get()[unique_id_] = this;
 }