DM: duh, don't calculate digests unless we're going to look at them.

dm/DMUtil.cpp

 #include "DMUtil.h"
 
 namespace DM {
 
 SkString underJoin(const char* a, const char* b) {
     SkString s;
     s.appendf("%s_%s", a, b);
     return s;
 }
 
 SkString png(SkString s) {
     s.appendf(".png");
     return s;
 }
 
-bool meetsExpectations(const skiagm::Expectations& expectations,
-                       const skiagm::GmResultDigest& digest) {
-    return expectations.ignoreFailure()
-        || expectations.empty()
-        || expectations.match(digest);
+bool meetsExpectations(const skiagm::Expectations& expectations, const SkBitmap bitmap) {
+    if (expectations.ignoreFailure() || expectations.empty()) {
+        return true;
+    }
+    const skiagm::GmResultDigest digest(bitmap);
+    return expectations.match(digest);
 }
 
 }  // namespace DM