Fix exception where no viewport was set in QuadView::drawDeviceViewport
Fix exception where no viewport was set in QuadView::drawDeviceViewport

If drawDeviceViewport_ was called and a viewport was not available,
we would throw an exception when calculating
getDeviceLineWidthAssumingTransformIsApplied. This patch skips the
viewport stroking when a viewport is not available.

BUG=

Review URL: https://codereview.appspot.com/9979052

git-svn-id: 3a56fcae908c7e16d23cb53443ea4795ac387cf2@603 0e6d7f2b-9903-5b78-7403-59d27f066143

bpsinc-native/src_third_party_trace-viewer,bpsinc-native/src_third_party_trace-viewer,bpsinc-native/src_third_party_trace-viewer,bpsinc-native/src_third_party_trace-viewer