Revert of SkThreadPool ~~> SkTaskGroup (patchset #4 id:60001 of https://codereview.chromium.org/531653002/)

Reason for revert:
Leaks, leaks, leaks.

Original issue's description:
> SkThreadPool ~~> SkTaskGroup
>
> SkTaskGroup is like SkThreadPool except the threads stay in
> one global pool.  Each SkTaskGroup itself is tiny (4 bytes)
> and its wait() method applies only to tasks add()ed to that
> instance, not the whole thread pool.
>
> This means we don't need to bring up new thread pools when
> tests themselves want to use multithreading (e.g. pathops,
> quilt).  We just create a new SkTaskGroup and wait for that
> to complete.  This should be more efficient, and allow us
> to expand where we use threads to really latency sensitive
> places.  E.g. we can probably now use these in nanobench
> for CPU .skp rendering.
>
> Now that all threads are sharing the same pool, I think we
> can remove most of the custom mechanism pathops tests use
> to control threading.  They'll just ride on the global pool
> with all other tests now.
>
> This (temporarily?) removes the GPU multithreading feature
> from DM, which we don't use.
>
> On my desktop, DM runs a little faster (57s -> 55s) in
> Debug, and a lot faster in Release (36s -> 24s).  The bots
> show speedups of similar proportions, cutting more than a
> minute off the N4/Release and Win7/Debug runtimes.
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/9c7207b5dc71dc5a96a2eb107d401133333d5b6f

R=caryclark@google.com, bsalomon@google.com, bungeman@google.com, reed@google.com, mtklein@chromium.org
TBR=bsalomon@google.com, bungeman@google.com, caryclark@google.com, mtklein@chromium.org, reed@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Author: mtklein@google.com

Review URL: https://codereview.chromium.org/533393002

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/PathOpsExtendedTest.h b/tests/PathOpsExtendedTest.h
index a854410139..5f3413c572 100644
--- a/tests/PathOpsExtendedTest.h
+++ b/tests/PathOpsExtendedTest.h
@@ -36,7 +36,7 @@ extern bool testSimplify(SkPath& path, bool useXor, SkPath& out, PathOpsThreadSt
                          const char* pathStr);
 extern bool testSimplify(skiatest::Reporter* reporter, const SkPath& path, const char* filename);
 
-void initializeTests(skiatest::Reporter* reporter, const char* testName);
+int initializeTests(skiatest::Reporter* reporter, const char* testName);
 void outputProgress(char* ramStr, const char* pathStr, SkPath::FillType );
 void outputProgress(char* ramStr, const char* pathStr, SkPathOp op);