When an activity sets FLAG_FULLSCREEN on its window, Android assumes
that the window size will always be the same as the screen size. This
causes the window to scroll instead of resizing when the soft keyboard
comes up, which (according to a quick Google search) isn't the behavior
most developers are expecting.
This patch implements an ugly workaround: extend the root element of the
layout (in our case, a LinearLayout) to hook into the onMeasure()
callback, which is called when the window size changes, so that we can
resize ourselves when the window size changes.
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