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, 2 insertions, 2 deletions

diff --git a/tests/PathOpsQuadLineIntersectionThreadedTest.cpp b/tests/PathOpsQuadLineIntersectionThreadedTest.cpp
index 7e33b7b374..fd7581fa58 100644
--- a/tests/PathOpsQuadLineIntersectionThreadedTest.cpp
+++ b/tests/PathOpsQuadLineIntersectionThreadedTest.cpp
@@ -111,8 +111,8 @@ static void testQuadLineIntersectMain(PathOpsThreadState* data)
 }
 
 DEF_TEST(PathOpsQuadLineIntersectionThreaded, reporter) {
-    initializeTests(reporter, "testQuadLineIntersect");
-    PathOpsThreadedTestRunner testRunner(reporter);
+    int threadCount = initializeTests(reporter, "testQuadLineIntersect");
+    PathOpsThreadedTestRunner testRunner(reporter, threadCount);
     for (int a = 0; a < 16; ++a) {
         for (int b = 0 ; b < 16; ++b) {
             for (int c = 0 ; c < 16; ++c) {