How to reproduce:
1. Create a new Unity project
2. Open Profiler Window
3. Enter Play mode and wait until the whole Profiler window is covered with data (takes about 5 seconds)
4. Navigate to Profiler Window - > Memory tab and change data display mode from Simple to Detailed
5. In Profiler Window, press 'Take Sample: Editor'
6. In Profiler Window, inspect value located in Other -> Profiling () -> ProfilerSession

Expected result: ProfilerSession is about 30Mb
Actual result: ProfilerSession is about 3Gb

Reproducible with: 2018.3.0b1, 2018.3.0b2, 2019.1.0a1
Not reproducible with: 2017.1.5f1, 2017.4.11f1, 2018.2.8f1, 2018.3.0a11