Define TRACE_OUTPUT_FILE macro to change filename. Default remains "debug.txt" for Visual Studio solution based build. Gyp based build uses "angle-debug.txt".

Review URL: http://codereview.appspot.com/2327043

git-svn-id: https://angleproject.googlecode.com/svn/trunk@445 736b8ea6-26fd-11df-bfd4-992fa37f6226