Revert of SkThreadPool ~~> SkTaskGroup

dm/DMTestTask.cpp

Index: dm/DMTestTask.cpp
diff --git a/dm/DMTestTask.cpp b/dm/DMTestTask.cpp
index ad0c3fb4f3d8cf3fbf0e45cf896f4f9ce55d604b..9e7f41e7d0991d39159d9e4ce104491319727c48 100644
--- a/dm/DMTestTask.cpp
+++ b/dm/DMTestTask.cpp
@@ -3,11 +3,17 @@
 #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) {