Add SkMiniData.

tests/MiniDataTest.cpp

+#include "SkMiniData.h"
+#include "Test.h"
+
+DEF_TEST(MiniData, r) {
+    static const char* s = "abcdefghijklmnopqrstuvwxyz";
+
+    for (size_t len = 0; len <= 26; len++) {
+        SkMiniData md(s, len);
+        REPORTER_ASSERT(r, md.len() == len);
+        REPORTER_ASSERT(r, 0 == memcmp(md.data(), s, len));
+
+        SkMiniData copy(md);
+        REPORTER_ASSERT(r, copy.len() == len);
+        REPORTER_ASSERT(r, 0 == memcmp(copy.data(), s, len));
+    }
+}