Remove mutex around image decoding in skpdiff.

tools/skpdiff/SkDiffContext.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 "SkBitmap.h"
 #include "SkImageDecoder.h"
 #include "SkOSFile.h"
@@ skipping 54 matching lines @@
         return b;
     } else {
         return a;
     }
 }
 
 void SkDiffContext::addDiff(const char* baselinePath, const char* testPath) {
     // Load the images at the paths
     SkBitmap baselineBitmap;
     SkBitmap testBitmap;
-    SkAutoMutexAcquire imageLock(fImageMutex);
     if (!SkImageDecoder::DecodeFile(baselinePath, &baselineBitmap)) {
         SkDebugf("Failed to load bitmap \"%s\"\n", baselinePath);
         return;
     }
     if (!SkImageDecoder::DecodeFile(testPath, &testBitmap)) {
         SkDebugf("Failed to load bitmap \"%s\"\n", testPath);
         return;
     }
-    imageLock.release();
 
     // Setup a record for this diff
     fRecordMutex.acquire();
     DiffRecord* newRecord = fRecords.addToHead(DiffRecord());
     fRecordMutex.release();
 
     // compute the common name
     SkString baseName = SkOSPath::SkBasename(baselinePath);
     SkString testName = SkOSPath::SkBasename(testPath);
     newRecord->fCommonName = get_common_prefix(baseName, testName);
@@ skipping 261 matching lines @@
         for (int i = 0; i < cntColumns; i++) {
             SkString str;
             str.printf(", %f", values[i]);
             stream.writeText(str.c_str());
         }
         stream.writeText("\n");
 
         currentRecord = iter2.next();
     }
 }