Code:  TaskService::TaskService()
    : next_instance_id_(0), bound_instance_id_(kInvalidInstanceId) {}

Commit Message: Change ReadWriteLock to Lock+ConditionVariable in TaskService

There are non-trivial performance implications of using shared
SRWLocking on Windows as more state has to be checked.

Since there are only two uses of the ReadWriteLock in Chromium after
over 1 year, the decision is to remove it.

BUG=758721

Change-Id: I84d1987d7b624a89e896eb37184ee50845c39d80
Reviewed-on: https://chromium-review.googlesource.com/634423
Commit-Queue: Robert Liao <robliao@chromium.org>
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Reviewed-by: Francois Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#497632}
CWE ID: CWE-20
 TaskService::TaskService()
