Revert of SkThreadPool ~~> SkTaskGroup

dm/DMTestTask.cpp

 #include "DMTestTask.h"
 #include "DMUtil.h"
 #include "SkCommandLineFlags.h"
 #include "SkCommonFlags.h"
 
-DEFINE_bool2(pathOpsExtended, x, false, "Run extended pathOps tests.");
+// When PathOps threaded tests get going, they're briefly a big consumer of lots of RAM.
+// We disable the internal threading there by default on 32-bit builds.
+static const bool is32Bit = sizeof(void*) == 4;
+
+DEFINE_bool2(pathOpsExtended,     x, false, "Run extended pathOps tests.");
+DEFINE_bool2(pathOpsSingleThread, z, is32Bit, "Disallow pathOps tests from using threads.");
 
 namespace DM {
 
 bool TestReporter::allowExtendedTest() const { return FLAGS_pathOpsExtended; }
+bool TestReporter::allowThreaded()     const { return !FLAGS_pathOpsSingleThread; }
 bool TestReporter::verbose()           const { return FLAGS_veryVerbose; }
 
 static SkString test_name(const char* name) {
     SkString result("test ");
     result.append(name);
     return result;
 }
 
 CpuTestTask::CpuTestTask(Reporter* reporter,
                          TaskRunner* taskRunner,
@@ skipping 25 matching lines @@
     if (!fTest->passed()) {
         this->fail(fTestReporter.failure());
     }
 }
 
 bool GpuTestTask::shouldSkip() const {
     return kGPUDisabled;
 }
 
 }  // namespace DM