fix multithread related crashes in skpdiff

BUG=skia:1798
R=mtklein@google.com, scroggo@google.com

Review URL: https://codereview.chromium.org/60833002

git-svn-id: http://skia.googlecode.com/svn/trunk@12252 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tools/skpdiff/SkImageDiffer.cpp b/tools/skpdiff/SkImageDiffer.cpp
index 40a34da..215a799 100644
--- a/tools/skpdiff/SkImageDiffer.cpp
+++ b/tools/skpdiff/SkImageDiffer.cpp
@@ -14,25 +14,10 @@
 const double SkImageDiffer::RESULT_CORRECT = 1.0f;
 const double SkImageDiffer::RESULT_INCORRECT = 0.0f;
 
-SkImageDiffer::SkImageDiffer()
-    : fIsGood(true) {
+SkImageDiffer::SkImageDiffer() {
 
 }
 
 SkImageDiffer::~SkImageDiffer() {
 
 }
-
-int SkImageDiffer::queueDiffOfFile(const char baseline[], const char test[]) {
-    SkBitmap baselineBitmap;
-    SkBitmap testBitmap;
-    if (!SkImageDecoder::DecodeFile(baseline, &baselineBitmap)) {
-        SkDebugf("Failed to load bitmap \"%s\"\n", baseline);
-        return -1;
-    }
-    if (!SkImageDecoder::DecodeFile(test, &testBitmap)) {
-        SkDebugf("Failed to load bitmap \"%s\"\n", test);
-        return -1;
-    }
-    return this->queueDiff(&baselineBitmap, &testBitmap);
-}