trace_processor: add missing file to BUILD.gn
trace_processor: add missing file to BUILD.gn

TBR=hjd
Change-Id: I2bfe32c724bd47dd170272bdf9ffa45e62cdad08

google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto