Implement accessibility support for CSS-transformed iframes.

content/renderer/accessibility/blink_ax_tree_source.cc

Index: content/renderer/accessibility/blink_ax_tree_source.cc
diff --git a/content/renderer/accessibility/blink_ax_tree_source.cc b/content/renderer/accessibility/blink_ax_tree_source.cc
index 914310dbc9c81d07c687f61f651c15bccbfcad31..ac907ab1f406e9439be257da27e283e4c71f01e8 100644
--- a/content/renderer/accessibility/blink_ax_tree_source.cc
+++ b/content/renderer/accessibility/blink_ax_tree_source.cc
@@ -533,8 +533,11 @@ void BlinkAXTreeSource::SerializeNode(blink::WebAXObject src,
                            src.minValueForRange());
   }
 
-  if (dst->role == ui::AX_ROLE_WEB_AREA)
+  if (dst->role == ui::AX_ROLE_WEB_AREA) {
     dst->AddStringAttribute(ui::AX_ATTR_HTML_TAG, "#document");
+    dst->transform.reset(
+        new gfx::Transform(src.transformFromLocalParentFrame()));
+  }
 
   if (dst->role == ui::AX_ROLE_TABLE) {
     int column_count = src.columnCount();