DM: go back to memcmp for BitmapsEqual

dm/DMUtil.cpp

 #include "DMUtil.h"
 
 #include "SkColorPriv.h"
 #include "SkPicture.h"
 #include "SkPictureRecorder.h"
 
 namespace DM {
 
 SkString UnderJoin(const char* a, const char* b) {
     SkString s;
@@ skipping 66 matching lines @@
         const uint8_t* bBytes = (const uint8_t*)b.getPixels();
         for (size_t i = 0; i < a.getSize(); i++) {
             max = SkTMax(max, abs_diff(aBytes[i], bBytes[i]));
         }
     }
 
     return max;
 }
 
 bool BitmapsEqual(const SkBitmap& a, const SkBitmap& b) {
-    return a.info() == b.info() && 0 == MaxComponentDifference(a, b);
+    if (a.info() != b.info()) {
+        return false;
+    }
+    const SkAutoLockPixels lockA(a), lockB(b);
+    return 0 == memcmp(a.getPixels(), b.getPixels(), a.getSize());
 }
 
 }  // namespace DM