Cache names used when converted to JS format.
Cache names used when converted to JS format.

We converte all key arguments to camel case before using them. This CL
adds a cache of the converted names so we don't repeat the same converision
work over and over again.

On my Mac Air this takes the time done in the preinit stage of importTraces
from ~1550ms to ~950ms.

BUG=211

Review URL: https://codereview.appspot.com/9878044
danbeam/catapult,scottmcmaster/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,scottmcmaster/catapult,catapult-project/catapult,sahiljain/catapult,sahiljain/catapult,SummerLW/Perf-Insight-Report,0x90sled/catapult,dstockwell/catapult,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,benschmaus/catapult,vmpstr/trace-viewer,dstockwell/catapult,SummerLW/Perf-Insight-Report,benschmaus/catapult,modulexcite/catapult,SummerLW/Perf-Insight-Report,SummerLW/Perf-Insight-Report,dstockwell/catapult,0x90sled/catapult,zeptonaut/catapult,modulexcite/catapult,zeptonaut/catapult,benschmaus/catapult,catapult-project/catapult-csm,benschmaus/catapult,SummerLW/Perf-Insight-Report,danbeam/catapult,dstockwell/catapult,modulexcite/catapult,catapult-project/catapult,benschmaus/catapult,zeptonaut/catapult,vmpstr/trace-viewer,catapult-project/catapult-csm,sahiljain/catapult,sahiljain/catapult,benschmaus/catapult,benschmaus/catapult,sahiljain/catapult,danbeam/catapult,danbeam/catapult,vmpstr/trace-viewer,catapult-project/catapult,SummerLW/Perf-Insight-Report,0x90sled/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,scottmcmaster/catapult,catapult-project/catapult-csm,catapult-project/catapult