Bug 1417327 part 3: Accessible handler: Fix cache for IAccessible::accDefaultAction and use it for IAccessibleAction::name(0). r=MarcoZ

1. Bug 1363595 added support for retrieving accDefaultAction from the cache, but the value was never cached in the first place.
This would have meant that accDefaultAction was returning nothing to clients.

2. Since accDefaultAction is the name of the first action, we can also use this cached value for IAccessibleAction::name for index 0.

MozReview-Commit-ID: 6PGRH45kKdB

UltraBlame original commit: f9111cd04f8cc3b2e7a3c559b8284c0525c7c098

Author: marco-c

accessible/ipc/win/HandlerProvider.cpp

@@ -315,6 +315,11 @@ HandlerProvider::BuildDynamicIA2Data(DynamicIA2Data* aOutIA2Data)
     return;
   }
 
+  hr = target->get_accDefaultAction(kChildIdSelf, &aOutIA2Data->mDefaultAction);
+  if (FAILED(hr)) {
+    return;
+  }
+
   hr = target->get_accChildCount(&aOutIA2Data->mChildCount);
   if (FAILED(hr)) {
     return;

accessible/ipc/win/handler/AccessibleHandler.cpp

@@ -1280,6 +1280,24 @@ AccessibleHandler::get_keyBinding(long actionIndex,
 HRESULT
 AccessibleHandler::get_name(long actionIndex, BSTR* name)
 {
+  if (!name) {
+    return E_INVALIDARG;
+  }
+
+  if (HasPayload()) {
+    if (actionIndex >= mCachedData.mDynamicData.mNActions) {
+      
+      return E_INVALIDARG;
+    }
+
+    if (actionIndex == 0) {
+      
+      GET_BSTR(mDefaultAction, *name);
+      return S_OK;
+    }
+  }
+
+  
   HRESULT hr = ResolveIAHyperlink();
   if (FAILED(hr)) {
     return hr;