The compilation trace lists functions that will be compiled in the core
snapshot. It is derived by unioning the output of Dart_SaveCompilationTrace
after startup from a few apps.

To update this trace.
  - Replace the existing trace with an empty file.
  - In //topaz/runtime/flutter_runner/engine.cc, change kCompilationTraceDelayInSeconds to a non-zero value.
  - Build, run a few apps, and add the log output to the trace.
  - Remove lines that aren't for dart: libraries.