Revert "Modify AXObjectCache to enqueue updates and notifications until the end of the document lifecycle."

This reverts commit 454b3b99346bd2546edfd1b4b10c28d20d351e46.

Reason for revert:

Seems to break
content/test/data/accessibility/events/aria-combo-box-delay-add-list.html

On Win 7. The test is flaky.

EVENT_OBJECT_FOCUS on <li#op1> role=ROLE_SYSTEM_LISTITEM name="Apple" SELECTED,FOCUSED,FOCUSABLE,SELECTABLE PosInSet=1 SetSize=1
IA2_EVENT_ACTIVE_DESCENDANT_CHANGED on <input> role=ROLE_SYSTEM_COMBOBOX EXPANDED,FOCUSABLE,HASPOPUP IA2_STATE_EDITABLE,IA2_STATE_SELECTABLE_TEXT,IA2_STATE_SINGLE_LINE,IA2_STATE_SUPPORTS_AUTOCOMPLETION
IA2_EVENT_TEXT_INSERTED on <div#container> role=DIV new_text={'<obj>' start=0 end=1}

The first two events are missing after this patch landed, but should have been there.


Original change's description:
> Modify AXObjectCache to enqueue updates and notifications until the end of the document lifecycle.
> 
> This is to defer any calls to tree traversal code until the DOM and Layout trees are in a clean state. This will facilitate modifying the accessibility tree code to walk the composed DOM tree rather than the layout tree.
> 
> Bug: 835455
> Change-Id: Idb2b32ee72b15ae5a56db8b0d4a613a081d9b27f
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1369489
> Commit-Queue: Alice Boxhall <aboxhall@chromium.org>
> Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
> Reviewed-by: Emil A Eklund <eae@chromium.org>
> Reviewed-by: Stefan Zager <szager@chromium.org>
> Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#642846}

TBR=dmazzoni@chromium.org,kinuko@chromium.org,szager@chromium.org,vmpstr@chromium.org,aboxhall@chromium.org,eae@chromium.org

Change-Id: I837121af87c4b8f2d86dff946a0366cdef5764b5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 835455
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1534144
Reviewed-by: Nektarios Paisios <nektar@chromium.org>
Commit-Queue: Nektarios Paisios <nektar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642956}
58 files changed