DM: some refactoring

dm/DMChecksumTask.cpp

Index: dm/DMChecksumTask.cpp
diff --git a/dm/DMChecksumTask.cpp b/dm/DMChecksumTask.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..0d9dce7fd1f85ff28c6ad62072aa87bf5adf7fee
--- /dev/null
+++ b/dm/DMChecksumTask.cpp
@@ -0,0 +1,26 @@
+#include "DMChecksumTask.h"
+#include "DMUtil.h"
+
+namespace DM {
+
+ChecksumTask::ChecksumTask(const Task& parent,
+                           skiagm::Expectations expectations,
+                           SkBitmap bitmap)
+    : Task(parent)
+    , fName(parent.name())  // Masquerade as parent so failures are attributed to it.
+    , fExpectations(expectations)
+    , fBitmap(bitmap)

[epoger, 2013/11/26 17:55:22]

I take it that copying the SkBitmap struct is pretty cheap?  Otherwise, given
that you only use the digest anyway, it might be better to construct this using
the digest instead.

[bsalomon, 2013/11/26 18:21:52]

bitmap is very shallow.

[mtklein, 2013/11/26 18:25:30]

Yes, copying SkBitmap is trivially cheap.  This class pretty much just exists to
delay calculating the digest until we're certain it's needed (line 20), as
that's the really expensive part.

+    {}
+
+void ChecksumTask::draw() {
+    if (fExpectations.ignoreFailure() || fExpectations.empty()) {
+        return;
+    }
+
+    const skiagm::GmResultDigest digest(fBitmap);
+    if (!fExpectations.match(digest)) {
+        this->fail();
+    }
+}
+
+}  // namespace DM