Keep track of fixed positioning in accessibility tree.

ui/accessibility/ax_node_data.cc

Index: ui/accessibility/ax_node_data.cc
diff --git a/ui/accessibility/ax_node_data.cc b/ui/accessibility/ax_node_data.cc
index eedfdd982913d7158f5738022b0b44f64aad3118..40b7bf421975fb7c1d7f87c71dd3786affe5f458 100644
--- a/ui/accessibility/ax_node_data.cc
+++ b/ui/accessibility/ax_node_data.cc
@@ -201,7 +201,8 @@ AXNodeData::AXNodeData()
       role(AX_ROLE_UNKNOWN),
       state(AX_STATE_NONE),
       actions(AX_ACTION_NONE),
-      offset_container_id(-1) {}
+      offset_container_id(-1),
+      is_fixed_positioned(false) {}
 
 AXNodeData::~AXNodeData() {
 }
@@ -223,6 +224,7 @@ AXNodeData::AXNodeData(const AXNodeData& other) {
   offset_container_id = other.offset_container_id;
   if (other.transform)
     transform.reset(new gfx::Transform(*other.transform));
+  is_fixed_positioned = other.is_fixed_positioned;
 }
 
 AXNodeData& AXNodeData::operator=(AXNodeData other) {
@@ -244,6 +246,7 @@ AXNodeData& AXNodeData::operator=(AXNodeData other) {
     transform.reset(new gfx::Transform(*other.transform));
   else
     transform.reset(nullptr);
+  is_fixed_positioned = other.is_fixed_positioned;
   return *this;
 }
 
@@ -558,6 +561,9 @@ std::string AXNodeData::ToString() const {
   if (transform && !transform->IsIdentity())
     result += " transform=" + transform->ToString();
 
+  if (is_fixed_positioned)
+    result += " is_fixed_positioned";
+
   for (size_t i = 0; i < int_attributes.size(); ++i) {
     std::string value = IntToString(int_attributes[i].second);
     switch (int_attributes[i].first) {