Speculative revert to diagnose crash in chrome. Revert "Add SkCachedData and use it for SkMipMap"

This reverts commit 92561a0b99ad6c08ab7a11dd1872f028199392e9.

crasher in question:
https://code.google.com/p/chromium/issues/detail?id=420178

Review URL: https://codereview.chromium.org/617613003
diff --git a/tests/MipMapTest.cpp b/tests/MipMapTest.cpp
index c8396ef..33f4672 100644
--- a/tests/MipMapTest.cpp
+++ b/tests/MipMapTest.cpp
@@ -25,7 +25,7 @@
 
     for (int i = 0; i < 500; ++i) {
         make_bitmap(&bm, rand);
-        SkAutoTUnref<SkMipMap> mm(SkMipMap::Build(bm, NULL));
+        SkAutoTUnref<SkMipMap> mm(SkMipMap::Build(bm));
 
         REPORTER_ASSERT(reporter, !mm->extractLevel(SK_Scalar1, NULL));
         REPORTER_ASSERT(reporter, !mm->extractLevel(SK_Scalar1 * 2, NULL));