Remove mutex around image decoding in skpdiff.

tools/skpdiff/SkDiffContext.cpp

Index: tools/skpdiff/SkDiffContext.cpp
diff --git a/tools/skpdiff/SkDiffContext.cpp b/tools/skpdiff/SkDiffContext.cpp
index f64aeac2acd8fb974c36ba37a11d9bd95636a7ef..dde091ac4ee0265b01485a2bbb2cade6b5bcd9a2 100644
--- a/tools/skpdiff/SkDiffContext.cpp
+++ b/tools/skpdiff/SkDiffContext.cpp
@@ -72,7 +72,6 @@ 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;
@@ -81,7 +80,6 @@ void SkDiffContext::addDiff(const char* baselinePath, const char* testPath) {
         SkDebugf("Failed to load bitmap \"%s\"\n", testPath);
         return;
     }
-    imageLock.release();
 
     // Setup a record for this diff
     fRecordMutex.acquire();