Handle collapsed tracks when drawing flow arrows.
Handle collapsed tracks when drawing flow arrows.

Currently, if a track is collapsed the flow line will end up drawing from or
too the top of the screen since the bounding rect will be [0, 0, 0, 0]. With
this CL, we detected if our parent Process track is not expanded and, if so,
we draw the flow arrow from the bottom of the Process bar line.

BUG=trace-viewer:359
R=nduca@chromium.org

Review URL: https://codereview.appspot.com/12931043

git-svn-id: 3a56fcae908c7e16d23cb53443ea4795ac387cf2@892 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