Use IAccessible2 to detect screen reader in Win Aura

Use IAccessible2 to detect screen reader in Win Aura.

See bug for context. This change makes calling
an IAccessible2 API on the web content's root
accessible object enable full web accessibility
support. This supports popular Windows screen readers
but won't enable accessibility under other
circumstances when we don't need it.

However, this doesn't always detect the screen
reader right away when the app opens, so we also
modify Views accessibility to detect IAccessible2
and query the IAccessible2 API on each web view.
That catches use of IAccessible2 immediately.

BUG=292719
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=223416

[sky, 2013-09-16 17:29:30]

LGTM

[David Tseng, 2013-09-16 18:51:28]

LGTM

Just one question.

Index: content/browser/accessibility/browser_accessibility_win.cc
diff --git a/content/browser/accessibility/browser_accessibility_win.cc
b/content/browser/accessibility/browser_accessibility_win.cc
index
b5c8fd3c90dc8afb51505f9e7751b25afded305f..df3263e845ddfb2cc82fe58cb5ce1b117d08bcda
100644
--- a/content/browser/accessibility/browser_accessibility_win.cc
+++ b/content/browser/accessibility/browser_accessibility_win.cc
@@ -15,6 +15,7 @@
 #include "base/win/scoped_comptr.h"
 #include "base/win/windows_version.h"
 #include
"content/browser/accessibility/browser_accessibility_manager_win.h"
+#include "content/browser/accessibility/browser_accessibility_state_impl.h"
 #include "content/common/accessibility_messages.h"
 #include "content/public/common/content_client.h"
 #include "ui/base/accessibility/accessible_text_utils.h"
@@ -2651,6 +2652,12 @@ STDMETHODIMP
BrowserAccessibilityWin::QueryService(REFGUID guidService,
   if (!instance_active_)
     return E_FAIL;

+  // The system uses IAccessible APIs for many purposes, but only
+  // assistive technology like screen readers uses IAccessible2.
+  // Enable full accessibility support when IAccessible2 APIs are queried.
+  if (riid == IID_IAccessible2)
+    BrowserAccessibilityStateImpl::GetInstance()->EnableAccessibility();
+

Would this mean that once accessibility is enabled, it never turns off?
(i.e. if a screen reader requests the IAccessible2 interface and is then
some time in the future turned off, we would still have accessibility
detected set).


On Mon, Sep 16, 2013 at 10:29 AM, <sky@chromium.org> wrote:

> LGTM
>
>
https://codereview.chromium.**org/23531055/<https://codereview.chromium.org/2...
>

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[dmazzoni, 2013-09-16 18:55:58]

On 2013/09/16 18:51:28, David Tseng wrote:
> Would this mean that once accessibility is enabled, it never turns off?

Yes, this is bug 251382. That's not a change from the current behavior.
I'd love your thoughts on how we might be able to fix it.

[commit-bot: I haz the power, 2013-09-16 18:56:19]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dmazzoni@chromium.org/23531055/1

[commit-bot: I haz the power, 2013-09-16 21:20:47]

Change committed as 223416