Fix a use after free crasher in the BrowserAccessibilityManagerWinTest.TestAccessibleHWND test.

Fix a use after free crasher in the BrowserAccessibilityManagerWinTest.TestAccessibleHWND test.

The crash occurs because a scoped_ptr instance which holds the TestLegacyRenderWidgetHostHWND class
is left with a dangling pointer to the LegacyRenderWidgetHostHWND instance which is destroyed via
DestroyWindow.

Fix is to first reset the scoped_ptr which in turn destroys the legacy window and the instance.
The DestroyWindow call is removed as it is not needed anymore.

I also added a call to the CreateATLModuleIfNeeded helper function in BrowserAccessibility::Create as I was
hitting a crash due to a NULL AtlModule. We do this already in the ctor of the BrowserAccessibilityManagerWin
class. However that is too late as we have base classes which create COM objects.

This crash only happens in the component builds.

BUG=393228
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=282759

[dmazzoni, 2014-07-11 20:50:01]

lgtm

[ananta, 2014-07-11 20:50:22]

The CQ bit was checked by ananta@chromium.org

[commit-bot: I haz the power, 2014-07-11 20:51:29]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ananta@chromium.org/383263002/1

[commit-bot: I haz the power, 2014-07-12 00:48:12]

Change committed as 282759