DM: swizzle BGRA to RGBA before calculating pixel MD5.

dm/DM.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "CrashHandler.h"
 #include "DMJsonWriter.h"
 #include "DMSrcSink.h"
@@ skipping 497 matching lines @@
             }
             SkAutoTDelete<SkStreamAsset> data(stream.detachAsStream());
 
             SkString md5;
             if (!FLAGS_writePath.isEmpty() || !FLAGS_readPath.isEmpty()) {
                 SkMD5 hash;
                 if (data->getLength()) {
                     hash.writeStream(data, data->getLength());
                     data->rewind();
                 } else {
-                    hash.write(bitmap.getPixels(), bitmap.getSize());
+                    // If we're BGRA (Linux, Windows), swizzle over to RGBA (Mac, Android).
+                    // This helps eliminate multiple 0-pixel-diff hashes on gold.skia.org.
+                    // (Android's general slow speed breaks the tie arbitrarily in RGBA's favor.)
+                    // We might consider promoting 565 to RGBA too.
+                    if (bitmap.colorType() == kBGRA_8888_SkColorType) {
+                        SkBitmap swizzle;
+                        SkAssertResult(bitmap.copyTo(&swizzle, kRGBA_8888_SkColorType));
+                        hash.write(swizzle.getPixels(), swizzle.getSize());
+                    } else {
+                        hash.write(bitmap.getPixels(), bitmap.getSize());
+                    }
                 }
                 SkMD5::Digest digest;
                 hash.finish(digest);
                 for (int i = 0; i < 16; i++) {
                     md5.appendf("%02x", digest.data[i]);
                 }
             }
 
             if (!FLAGS_readPath.isEmpty() &&
                 !gGold.contains(Gold(task->sink.tag, task->src.tag,
@@ skipping 282 matching lines @@
     }
     return 0;
 }
 
 #if !defined(SK_BUILD_FOR_IOS)
 int main(int argc, char** argv) {
     SkCommandLineFlags::Parse(argc, argv);
     return dm_main();
 }
 #endif