Cherrypick: Don't send extra text changed AX events on Android

This is a clean Cherrypick of 2 CLs from chromium:
https://codereview.chromium.org/920623002
And https://codereview.chromium.org/922883002/

Original description:
Don't send extra text changed AX events on Android

This fix is small and safe, for merging. The reason this
was happening has to do with contenteditable support
and I'll follow up with a cleaner fix once this is merged.

BUG:19294187
Change-Id: Ifd0de22fdad20a917ca74174c90fce8bec7d87ad
diff --git a/content/browser/accessibility/browser_accessibility_manager_android.cc b/content/browser/accessibility/browser_accessibility_manager_android.cc
index fd4e0ff..0f9c701 100644
--- a/content/browser/accessibility/browser_accessibility_manager_android.cc
+++ b/content/browser/accessibility/browser_accessibility_manager_android.cc
@@ -173,10 +173,9 @@
       Java_BrowserAccessibilityManager_handleTextSelectionChanged(
           env, obj.obj(), node->GetId());
       break;
-    case ui::AX_EVENT_CHILDREN_CHANGED:
     case ui::AX_EVENT_TEXT_CHANGED:
     case ui::AX_EVENT_VALUE_CHANGED:
-      if (node->IsEditableText()) {
+      if (node->IsEditableText() && GetFocus(GetRoot()) == node) {
         Java_BrowserAccessibilityManager_handleEditableTextChanged(
             env, obj.obj(), node->GetId());
       } else if (android_node->IsSlider()) {