Allows the user to toggle the default mouse mode between pan and selection. The shift modifier now temporarily switches the mode to the alternative.
Allows the user to toggle the default mouse mode between pan and selection.
The shift modifier now temporarily switches the mode to the alternative.

R=nduca@chromium.org

Review URL: https://codereview.appspot.com/10750044
sahiljain/catapult,catapult-project/catapult-csm,0x90sled/catapult,modulexcite/catapult,catapult-project/catapult,catapult-project/catapult,sahiljain/catapult,vmpstr/trace-viewer,modulexcite/catapult,catapult-project/catapult,scottmcmaster/catapult,catapult-project/catapult,dstockwell/catapult,danbeam/catapult,benschmaus/catapult,scottmcmaster/catapult,catapult-project/catapult-csm,dstockwell/catapult,catapult-project/catapult-csm,sahiljain/catapult,benschmaus/catapult,benschmaus/catapult,0x90sled/catapult,dstockwell/catapult,zeptonaut/catapult,SummerLW/Perf-Insight-Report,catapult-project/catapult,danbeam/catapult,scottmcmaster/catapult,benschmaus/catapult,benschmaus/catapult,vmpstr/trace-viewer,zeptonaut/catapult,SummerLW/Perf-Insight-Report,SummerLW/Perf-Insight-Report,catapult-project/catapult,SummerLW/Perf-Insight-Report,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,sahiljain/catapult,danbeam/catapult,dstockwell/catapult,benschmaus/catapult,zeptonaut/catapult,SummerLW/Perf-Insight-Report,0x90sled/catapult,danbeam/catapult,catapult-project/catapult-csm,SummerLW/Perf-Insight-Report,catapult-project/catapult-csm,sahiljain/catapult,sahiljain/catapult,catapult-project/catapult,modulexcite/catapult,vmpstr/trace-viewer