Improve docs about runtime signalling. am: 31b44b3a70 am: 1afd8f6aaf
Improve docs about runtime signalling. am: 31b44b3a70 am: 1afd8f6aaf

Original change: https://android-review.googlesource.com/c/platform/external/perfetto/+/1454876

Change-Id: Ie54ed197e92cb5ee87bdd2e82f496018ea3a574d

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