SkStream Testing: fix bug in new unit test.

tests/StreamTest.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Resources.h"
 #include "SkData.h"
 #include "SkFrontBufferedStream.h"
@@ skipping 325 matching lines @@
     }
     stream_peek_test(rep, asset, expected);
 }
 
 namespace {
 class DumbStream : public SkStream {
 public:
     DumbStream(const uint8_t* data, size_t n)
         : fData(data), fCount(n), fIdx(0) {}
     size_t read(void* buffer, size_t size) override {
-        size_t c = SkTMin(fCount - fIdx, size);
-        if (c) {
-            memcpy(buffer, &fData[fIdx], size);
-            fIdx += c;
+        size_t copyCount = SkTMin(fCount - fIdx, size);
+        if (copyCount) {
+            memcpy(buffer, &fData[fIdx], copyCount);
+            fIdx += copyCount;
         }
-        return c;
+        return copyCount;
     }
     bool isAtEnd() const override {
-        return fCount > fIdx;
+        return fCount == fIdx;
     }
  private:
     const uint8_t* fData;
     size_t fCount, fIdx;
 };
 }  // namespace
 
 static void stream_copy_test(skiatest::Reporter* reporter,
                              const void* srcData,
                              size_t N,
@@ skipping 21 matching lines @@
     for (int j = 0; j < N; ++j) {
         src[j] = random.nextU() & 0xff;
     }
     // SkStreamCopy had two code paths; this test both.
     DumbStream dumbStream(src.get(), (size_t)N);
     stream_copy_test(reporter, src, N, &dumbStream);
     SkMemoryStream smartStream(src.get(), (size_t)N);
     stream_copy_test(reporter, src, N, &smartStream);
 
 }