Since we moved the mouse tracking out of the timeline_track_view the WASD-based zoom doesn't account for the mouse position. Consequently it always zooms in on the last (often incorrect) mouse position. This adds a mousemove listener to track the mouse at all times.
Since we moved the mouse tracking out of the timeline_track_view the WASD-based zoom doesn't account for the mouse position. Consequently it always zooms in on the last (often incorrect) mouse position. This adds a mousemove listener to track the mouse at all times.

R=dsinclair@chromium.org

Review URL: https://codereview.appspot.com/11459044
SummerLW/Perf-Insight-Report,zeptonaut/catapult,danbeam/catapult,vmpstr/trace-viewer,zeptonaut/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,0x90sled/catapult,0x90sled/catapult,scottmcmaster/catapult,vmpstr/trace-viewer,catapult-project/catapult-csm,danbeam/catapult,sahiljain/catapult,modulexcite/catapult,modulexcite/catapult,SummerLW/Perf-Insight-Report,catapult-project/catapult-csm,zeptonaut/catapult,dstockwell/catapult,sahiljain/catapult,SummerLW/Perf-Insight-Report,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult-csm,catapult-project/catapult,benschmaus/catapult,sahiljain/catapult,catapult-project/catapult,benschmaus/catapult,benschmaus/catapult,sahiljain/catapult,danbeam/catapult,dstockwell/catapult,catapult-project/catapult-csm,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult,scottmcmaster/catapult,sahiljain/catapult,catapult-project/catapult-csm,SummerLW/Perf-Insight-Report,catapult-project/catapult,0x90sled/catapult,catapult-project/catapult,benschmaus/catapult,dstockwell/catapult,scottmcmaster/catapult,vmpstr/trace-viewer,benschmaus/catapult,SummerLW/Perf-Insight-Report,dstockwell/catapult,SummerLW/Perf-Insight-Report,modulexcite/catapult,danbeam/catapult,benschmaus/catapult