DM: Add support for reading a directory of images with --expectations (-r).

dm/DMWriteTask.h

Index: dm/DMWriteTask.h
diff --git a/dm/DMWriteTask.h b/dm/DMWriteTask.h
index 82a26bc928bb7215c7ba1f03478c4b6c2f4a00ff..49a5c746a64fbed20a2ec6bb26860d349af58130 100644
--- a/dm/DMWriteTask.h
+++ b/dm/DMWriteTask.h
@@ -1,11 +1,13 @@
 #ifndef DMWriteTask_DEFINED
 #define DMWriteTask_DEFINED
 
+#include "DMExpectations.h"
 #include "DMTask.h"
 #include "SkBitmap.h"
 #include "SkString.h"
 #include "SkTArray.h"
 
+
 // Writes a bitmap to a file.
 
 namespace DM {
@@ -21,6 +23,16 @@ public:
     virtual bool shouldSkip() const SK_OVERRIDE;
     virtual SkString name() const SK_OVERRIDE;
 
+    // Reads image files WriteTask wrote under root and compares them with bitmap.
+    class Expectations : public DM::Expectations {
+    public:
+        explicit Expectations(const char* root) : fRoot(root) {}
+
+        bool check(const Task& task, SkBitmap bitmap) const SK_OVERRIDE;
+    private:
+        const char* fRoot;
+    };
+
 private:
     SkTArray<SkString> fSuffixes;
     SkString fGmName;