The surface created for the magnifier is larger than the magnifier
content, in order to leave space for drawing the shadow. In
I066082fb17cfb8c483c49b7011abfa9dca9de77a we made the elevation a
customizable property of Magnifier using the Builder class. However, the
buffer allocated for drawing the shadow remained a fixed value,
insufficient for large elevations, when shadows were getting clipped.
This CL fixes this, by making the allocated surface large enough to
accomodate the shadow.
Bug: none
Test: atest CtsWidgetTestCases:android.widget.cts.MagnifierTest
Change-Id: I462c50510820614dc033a42b347e9672ce39a4c6
bd391f9aa1