add initial support ofr multi-threaded execution

Review URL: https://codereview.chromium.org/27541003

git-svn-id: http://skia.googlecode.com/svn/trunk@11823 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tools/skpdiff/SkDiffContext.h b/tools/skpdiff/SkDiffContext.h
index 93354e8..20193b3 100644
--- a/tools/skpdiff/SkDiffContext.h
+++ b/tools/skpdiff/SkDiffContext.h
@@ -23,6 +23,8 @@
     SkDiffContext();
     ~SkDiffContext();
 
+    void setThreadCount(int threadCount) { fThreadCount = threadCount; }
+
     /**
      * Sets the differs to be used in each diff. Already started diffs will not retroactively use
      * these.
@@ -104,6 +106,7 @@
     };
 
     struct DiffRecord {
+        SkString           fDifferencePath;
         SkString           fBaselinePath;
         SkString               fTestPath;
         SkTArray<DiffData>        fDiffs;
@@ -117,6 +120,7 @@
 
     SkImageDiffer** fDiffers;
     int fDifferCount;
+    int fThreadCount;
 };
 
 #endif