TimelineSliceTrack should verify that its slices are monotonically increasing when assigned
TimelineSliceTrack should verify that its slices are monotonically increasing when assigned

BUG=22
TEST=timeline_track_test.html

Review URL: https://codereview.appspot.com/6401052
scottmcmaster/catapult,vmpstr/trace-viewer,catapult-project/catapult,danbeam/catapult,danbeam/catapult,sahiljain/catapult,catapult-project/catapult-csm,modulexcite/catapult,benschmaus/catapult,dstockwell/catapult,catapult-project/catapult,zeptonaut/catapult,dstockwell/catapult,sahiljain/catapult,catapult-project/catapult-csm,zeptonaut/catapult,scottmcmaster/catapult,vmpstr/trace-viewer,benschmaus/catapult,SummerLW/Perf-Insight-Report,benschmaus/catapult,SummerLW/Perf-Insight-Report,catapult-project/catapult-csm,modulexcite/catapult,sahiljain/catapult,catapult-project/catapult-csm,catapult-project/catapult,SummerLW/Perf-Insight-Report,catapult-project/catapult-csm,catapult-project/catapult,danbeam/catapult,0x90sled/catapult,catapult-project/catapult-csm,0x90sled/catapult,0x90sled/catapult,benschmaus/catapult,catapult-project/catapult-csm,sahiljain/catapult,modulexcite/catapult,benschmaus/catapult,scottmcmaster/catapult,catapult-project/catapult,danbeam/catapult,benschmaus/catapult,catapult-project/catapult,SummerLW/Perf-Insight-Report,dstockwell/catapult,catapult-project/catapult,dstockwell/catapult,vmpstr/trace-viewer,zeptonaut/catapult,SummerLW/Perf-Insight-Report,sahiljain/catapult,sahiljain/catapult,benschmaus/catapult,SummerLW/Perf-Insight-Report