Macbook Pro on Yosemite - screen going to black
That log shows few problems.

First you have continuous Crash ReportCrash[2551]: Saved crash report for mdworker32[2550] version 917.1 to /Users/TARINISHOME/Library/Logs/DiagnosticReports/mdworker32_2015-04-03-123458_Tarinis-MacBook-Pro.crash

That is the 


  mdworker32 is the 32 bit version metadata server worker process.
  mdworker is used by mds to scan and index files as a volume is mounted
  or a file changes.


So tell us what is connected to your system and Open that Crash report to look what is happening. 

I would also (temporary) disable any sharing.