DM: when 32-bit, disable pathops internal threading by default

Before this change, when limited to 4G, pathops threaded tests were the weak
link RAM-consumption-wise (in thread-local font caches) up until about 12
cores, where other problems begin to pile up too.

Tested by running:
    ulimit -Sv 4194304
    out/Debug/dm --threads N [--pathOpsSingleThread]

After this, we're _probably_ good to go on 32-bit machines with 8 cores.

BUG=skia:2478
R=borenet@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/265593003

git-svn-id: http://skia.googlecode.com/svn/trunk@14463 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/dm/DMTestTask.cpp b/dm/DMTestTask.cpp
index e16df98..f99abd0 100644
--- a/dm/DMTestTask.cpp
+++ b/dm/DMTestTask.cpp
@@ -2,8 +2,12 @@
 #include "DMUtil.h"
 #include "SkCommandLineFlags.h"
 
+// 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, false, "Disallow pathOps tests from using threads.");
+DEFINE_bool2(pathOpsSingleThread, z, is32Bit, "Disallow pathOps tests from using threads.");
 DEFINE_bool2(pathOpsVerbose,      V, false, "Tell pathOps tests to be verbose.");
 
 namespace DM {