Implement BrowserAccessibility accNavigate() in terms of AXPlatformNodeWin.

content/browser/accessibility/browser_accessibility_win.cc

Index: content/browser/accessibility/browser_accessibility_win.cc
diff --git a/content/browser/accessibility/browser_accessibility_win.cc b/content/browser/accessibility/browser_accessibility_win.cc
index d4a8d1fa4c3d11eaf568b897239c305326c4c4c1..87ae27f257e71819e8db89a87f66b70b16191302 100644
--- a/content/browser/accessibility/browser_accessibility_win.cc
+++ b/content/browser/accessibility/browser_accessibility_win.cc
@@ -495,13 +495,12 @@ STDMETHODIMP BrowserAccessibilityWin::accNavigate(LONG nav_dir,
   if (!target)
     return E_INVALIDARG;
 
-  if ((nav_dir == NAVDIR_LASTCHILD || nav_dir == NAVDIR_FIRSTCHILD) &&
-      start.lVal != CHILDID_SELF) {
-    // MSAA states that navigating to first/last child can only be from self.
-    return E_INVALIDARG;
+  // Forward all directions but NAVDIR_ to the platform node implementation.
+  if (nav_dir != NAVDIR_DOWN && nav_dir != NAVDIR_UP &&
+      nav_dir != NAVDIR_LEFT && nav_dir != NAVDIR_RIGHT) {
+    return target->GetPlatformNodeWin()->accNavigate(nav_dir, start, end);
   }
 
-  uint32_t child_count = target->PlatformChildCount();
   BrowserAccessibility* result = nullptr;
   switch (nav_dir) {
     case NAVDIR_DOWN:
@@ -518,20 +517,6 @@ STDMETHODIMP BrowserAccessibilityWin::accNavigate(LONG nav_dir,
       result = target->GetTableCell(GetTableRow(),
                                     GetTableColumn() + GetTableColumnSpan());
       break;
-    case NAVDIR_FIRSTCHILD:
-      if (child_count > 0)
-        result = target->PlatformGetChild(0);
-      break;
-    case NAVDIR_LASTCHILD:
-      if (child_count > 0)
-        result = target->PlatformGetChild(child_count - 1);
-      break;
-    case NAVDIR_NEXT:
-      result = target->GetNextSibling();
-      break;
-    case NAVDIR_PREVIOUS:
-      result = target->GetPreviousSibling();
-      break;
   }
 
   if (!result) {