Add missing import to generate_standalone_timeline_view.py
Add missing import to generate_standalone_timeline_view.py

TBR=nduca@chromium.org

Review URL: https://codereview.appspot.com/18390043
benschmaus/catapult,sahiljain/catapult,SummerLW/Perf-Insight-Report,danbeam/catapult,catapult-project/catapult,catapult-project/catapult,0x90sled/catapult,catapult-project/catapult,vmpstr/trace-viewer,catapult-project/catapult,dstockwell/catapult,danbeam/catapult,catapult-project/catapult-csm,vmpstr/trace-viewer,0x90sled/catapult,dstockwell/catapult,sahiljain/catapult,dstockwell/catapult,modulexcite/catapult,catapult-project/catapult-csm,scottmcmaster/catapult,modulexcite/catapult,benschmaus/catapult,benschmaus/catapult,benschmaus/catapult,benschmaus/catapult,SummerLW/Perf-Insight-Report,SummerLW/Perf-Insight-Report,zeptonaut/catapult,dstockwell/catapult,catapult-project/catapult-csm,sahiljain/catapult,sahiljain/catapult,catapult-project/catapult-csm,zeptonaut/catapult,danbeam/catapult,modulexcite/catapult,danbeam/catapult,catapult-project/catapult-csm,catapult-project/catapult,SummerLW/Perf-Insight-Report,scottmcmaster/catapult,benschmaus/catapult,vmpstr/trace-viewer,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,scottmcmaster/catapult,sahiljain/catapult,SummerLW/Perf-Insight-Report,SummerLW/Perf-Insight-Report,0x90sled/catapult,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult,zeptonaut/catapult