DevTools: Make children field of the CpuProfileNode optional in the protocol.

BUG=635947

Review-Url: https://codereview.chromium.org/2248963007
Cr-Original-Commit-Position: refs/heads/master@{#413276}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 6bdab9a3cd716bb9e2bc33384e605e068d134d77
2 files changed