Revert of Fire AX notifications on list box options.

Revert of Fire AX notifications on list box options. (patchset #7 id:120001 of https://codereview.chromium.org/1034493005/)

Reason for revert:
Suspect as cause of #1 crash in Windows canaries 44.0.2392.0 and 44.0.2393.0

BUG=484642
Original issue's description:
> Fire AX notifications on list box options.
> 
> Previously we just sent a single notification on the
> list box when the selection changed, now we send
> separate notifications on each option that changes
> state too.
> 
> BUG=323462
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=192997

TBR=mkwst@chromium.org,je_julie.kim@samsung.com,tkent@chromium.org,dmazzoni@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=323462

[mark a. foltz, 2015-05-06 22:25:12]

Created Revert of Fire AX notifications on list box options.

[commit-bot: I haz the power, 2015-05-06 22:25:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1127283002/1

[commit-bot: I haz the power, 2015-05-06 22:26:24]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-05-06 22:26:26]

Failed to apply patch for Source/core/html/HTMLSelectElement.cpp:
While running patch -p1 --forward --force --no-backup-if-mismatch;
  patching file Source/core/html/HTMLSelectElement.cpp
  Hunk #1 succeeded at 730 with fuzz 1.
  Hunk #2 FAILED at 970.
  1 out of 2 hunks FAILED -- saving rejects to file
Source/core/html/HTMLSelectElement.cpp.rej

Patch:       Source/core/html/HTMLSelectElement.cpp
Index: Source/core/html/HTMLSelectElement.cpp
diff --git a/Source/core/html/HTMLSelectElement.cpp
b/Source/core/html/HTMLSelectElement.cpp
index
2a5d6c9253a03401aba4172c36a807ce9f003f5c..d8eb4c116e4683ed3e38761b208b55c339c7dacf
100644
--- a/Source/core/html/HTMLSelectElement.cpp
+++ b/Source/core/html/HTMLSelectElement.cpp
@@ -730,7 +730,7 @@
         return;
     scrollToIndex(activeSelectionEndListIndex());
     if (AXObjectCache* cache = document().existingAXObjectCache())
-        cache->listboxActiveIndexChanged(this);
+        cache->selectedChildrenChanged(this);
 }
 
 void HTMLSelectElement::setOptionsChangedOnRenderer()
@@ -970,6 +970,9 @@
         if (LayoutObject* renderer = this->layoutObject()) {
             if (usesMenuList()) {
                 toLayoutMenuList(renderer)->didSetSelectedIndex(listIndex);
+            } else if (renderer->isListBox()) {
+                if (AXObjectCache* cache = document().existingAXObjectCache())
+                    cache->selectedChildrenChanged(this);
             }
         }
     }

[commit-bot: I haz the power, 2015-05-06 22:26:37]

The CQ bit was unchecked by commit-bot@chromium.org

[dmazzoni, 2015-05-06 22:30:34]

Other changes have landed on top of this one, reverting it will be nontrivial.

This is a one-line fix, let me fix it with a null check rather than a revert.