Fix GCC 'changes meaning of name' bug

Use explicit scope qualification in alias declaration.

Error example:
-c ../../ui/accessibility/platform/inspect/tree_formatter.cc -o obj/ui/accessibility/platform/platform/tree_formatter.o
In file included from ../../ui/accessibility/platform/inspect/tree_formatter.cc:5:
../../ui/accessibility/platform/inspect/tree_formatter.h:26:40: error: declaration of ‘using AXTreeSelector = struct ui::AXTreeSelector’ [-fpermissive]
   using AXTreeSelector = AXTreeSelector;

Bug: 819294
Change-Id: Ic604b34def922d5f6e9f5181cb2052433282c6fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2524535Reviewed-by: Joanmarie Diggs <jdiggs@igalia.com>
Commit-Queue: Joanmarie Diggs <jdiggs@igalia.com>
Cr-Commit-Position: refs/heads/master@{#825313}

ui/accessibility/platform/inspect/tree_formatter.h

@@ -23,9 +23,9 @@ class AXPlatformNodeDelegate;
 // implemented.
 class AX_EXPORT AXTreeFormatter {
  public:
-  using AXTreeSelector = AXTreeSelector;
-  using AXPropertyFilter = AXPropertyFilter;
-  using AXNodeFilter = AXNodeFilter;
+  using AXTreeSelector = ui::AXTreeSelector;
+  using AXPropertyFilter = ui::AXPropertyFilter;
+  using AXNodeFilter = ui::AXNodeFilter;
 
   virtual ~AXTreeFormatter() = default;