add const to encodePixels pixel parameter

tests/PictureTest.cpp

Index: tests/PictureTest.cpp
diff --git a/tests/PictureTest.cpp b/tests/PictureTest.cpp
index 2881e5f5a825b0e732664a23a30d6b93e4f58575..b98cc4680e1798e68605a6ef6fe62e5460fc1d45 100644
--- a/tests/PictureTest.cpp
+++ b/tests/PictureTest.cpp
@@ -1448,14 +1448,10 @@ static void test_bad_bitmap() {
 // FIXME: Share with PictureRenderer.cpp?
 class PngPixelSerializer : public SkPixelSerializer {
 public:
-    virtual bool onUseEncodedData(const void*, size_t) SK_OVERRIDE { return true; }
-    virtual SkData* onEncodePixels(const SkImageInfo& info, void* pixels,
-                                   size_t rowBytes) SK_OVERRIDE {
-        SkBitmap bm;
-        if (!bm.installPixels(info, pixels, rowBytes)) {
-            return NULL;
-        }
-        return SkImageEncoder::EncodeData(bm, SkImageEncoder::kPNG_Type, 100);
+    bool onUseEncodedData(const void*, size_t) SK_OVERRIDE { return true; }
+    SkData* onEncodePixels(const SkImageInfo& info, const void* pixels,
+                           size_t rowBytes) SK_OVERRIDE {
+        return SkImageEncoder::EncodeData(info, pixels, rowBytes, SkImageEncoder::kPNG_Type, 100);
     }
 };