This call from inspector side is redundant, V8 will clear all breakpoints on removing debug delegate in v8::internal::Debug::Unload method.

In any case for correct support of multiclient we need to clear breakpoints in V8DebuggerAgentImpl::disable method.

R=dgozman@chromium.org

Bug: v8:5510,chromium:652939
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I66f9b97797860bad28884a099928d54ac3560428
Reviewed-on: https://chromium-review.googlesource.com/592281
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47022}