Don't die(immediate) if from performTraversals.

The Drive application was calling PopupWindow.dismiss from within
onMeasure. This caused dispatchDetachedFromWindow to be called
from within performTraversals. Since dispatchDetachedFromWindow
destroys much of what performTraversals uses this was a disaster
waiting to happen.

This fix adds a check for seeing if die(immediate=true) is being
called from within performTraversals. If it is then die doesn't
execute doDie immediately, but instead treats it as a call to
die(immediate=false).

Fixes bug 6836841.

Change-Id: I833289e12c19fd33c17a715b2ed2adcf8388573a