DM: add --writePath

For fun, make the output prettier, hiding ", N failures" unless there is one.

BUG=
R=bsalomon@google.com

Review URL: https://codereview.chromium.org/29293003

git-svn-id: http://skia.googlecode.com/svn/trunk@11867 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/dm/DMGpuTask.cpp b/dm/DMGpuTask.cpp
index 6cf69ff..a002b95 100644
--- a/dm/DMGpuTask.cpp
+++ b/dm/DMGpuTask.cpp
@@ -2,6 +2,7 @@
 
 #include "DMComparisonTask.h"
 #include "DMUtil.h"
+#include "DMWriteTask.h"
 #include "SkCommandLineFlags.h"
 #include "SkGpuDevice.h"
 #include "SkTLS.h"
@@ -58,6 +59,7 @@
     // We offload checksum comparison to the main CPU threadpool.
     // This cuts run time by about 30%.
     this->spawnChild(SkNEW_ARGS(ComparisonTask, (*this, fExpectations, bitmap)));
+    this->spawnChild(SkNEW_ARGS(WriteTask, (*this, bitmap)));
 }
 
 bool GpuTask::shouldSkip() const {