Noting that xpath is disabled.
Caching colors on events/marks/timeranges and using integer colors.
This roughly doubles the speed of drawing large traces.
Removing a redundant statistics rebuild on startup.
Saves a second or two on initial display time for large traces.
Dropping the unused 'Value' from the EventStruct.
Merge pull request #251 from google/drawperf

Various performance improvements to drawing and loading.