bug 1262233 - stop implementing ProxyAccessible::EmbeddedChildAt() with a sync message r=lsocks

accessible/ipc/DocAccessibleChild.cpp

@@ -1845,21 +1845,6 @@ DocAccessibleChild::RecvTakeFocus(const uint64_t& aID)
   return true;
 }
 
-bool
-DocAccessibleChild::RecvEmbeddedChildAt(const uint64_t& aID,
-                                        const uint32_t& aIdx,
-                                        uint64_t* aChildID)
-{
-  *aChildID = 0;
-
-  Accessible* acc = IdToAccessible(aID);
-  if (!acc)
-    return true;
-
-  *aChildID = reinterpret_cast<uintptr_t>(acc->GetEmbeddedChildAt(aIdx));
-  return true;
-}
-
 bool
 DocAccessibleChild::RecvFocusedChild(const uint64_t& aID,
                                        uint64_t* aChild,

accessible/ipc/DocAccessibleChild.h

@@ -454,9 +454,6 @@ public:
 
   virtual bool RecvTakeFocus(const uint64_t& aID) override;
 
-  virtual bool RecvEmbeddedChildAt(const uint64_t& aID, const uint32_t& aIdx,
-                                   uint64_t* aChildID) override final;
-
   virtual bool RecvFocusedChild(const uint64_t& aID,
                                 uint64_t* aChild,
                                 bool* aOk) override;

accessible/ipc/PDocAccessible.ipdl

@@ -237,8 +237,6 @@ child:
   prio(high) sync Step(uint64_t aID) returns(double aStep);
 
   async TakeFocus(uint64_t aID);
-  prio(high) sync EmbeddedChildAt(uint64_t aID, uint32_t aChildIdx)
-    returns(uint64_t aChild);
   prio(high) sync FocusedChild(uint64_t aID)
     returns(uint64_t aChild, bool aOk);
 

accessible/ipc/ProxyAccessible.cpp

@@ -1065,17 +1065,20 @@ ProxyAccessible::IndexOfEmbeddedChild(const ProxyAccessible* aChild)
 ProxyAccessible*
 ProxyAccessible::EmbeddedChildAt(size_t aChildIdx)
 {
-  // For an outer doc the only child is a document, which is of course an
-  // embedded child.  Further asking the child process for the id of the child
-  // document won't work because the id of the child doc will be 0, which we
-  // would interpret as being our parent document.
-  if (mOuterDoc) {
-    return ChildAt(aChildIdx);
+  size_t index = 0, kids = mChildren.Length();
+  for (size_t i = 0; i < kids; i++) {
+    if (!mChildren[i]->IsEmbeddedObject()) {
+      continue;
+    }
+
+    if (index == aChildIdx) {
+      return mChildren[i];
+    }
+
+    index++;
   }
 
-  uint64_t childID;
-  Unused << mDoc->SendEmbeddedChildAt(mID, aChildIdx, &childID);
-  return mDoc->GetAccessible(childID);
+  return nullptr;
 }
 
 ProxyAccessible*