Integrate registry_hash_store_contents with the rest of tracked prefs.

components/user_prefs/tracked/registry_hash_store_contents_win_unittest.cc

Index: components/user_prefs/tracked/registry_hash_store_contents_win_unittest.cc
diff --git a/components/user_prefs/tracked/registry_hash_store_contents_win_unittest.cc b/components/user_prefs/tracked/registry_hash_store_contents_win_unittest.cc
index 5f2cbb052828fa561059324cb72db3a8f9e32f9c..f5b4837e904b79318d9d4ccc702fe105ec5a5419 100644
--- a/components/user_prefs/tracked/registry_hash_store_contents_win_unittest.cc
+++ b/components/user_prefs/tracked/registry_hash_store_contents_win_unittest.cc
@@ -16,9 +16,12 @@ namespace {
 constexpr base::char16 kRegistryPath[] = L"Foo\\TestStore";
 constexpr base::char16 kStoreKey[] = L"test_store_key";
 
-// MACs are 32 characters long.
-constexpr char kTestStringA[] = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
-constexpr char kTestStringB[] = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
+// MACs are 32 characters long, which stored in the registry are 64 characters
+// long due to 8-bit to 16-bit char conversion.

[gab, 2016/09/23 14:01:18]

This is still unexpected to me, i.e. this is passed to contents->SetMac() which
takes an std::string and as such I would think expects a 32-char string, no?

[proberge, 2016/09/23 15:24:34]

My bad, I completely misunderstood what was going on. SetMac() is called with a
64-char string. pref_hash_calculator generates a 32-char string, but then
base::HexEncode()s it.

base::HexEncode() turns it into a 64-char string:
https://cs.chromium.org/chromium/src/base/strings/string_number_conversions.c...

[gab, 2016/09/23 15:56:58]

Ah ok, now that makes more sense, thanks!

+constexpr char kTestStringA[] =
+    "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+constexpr char kTestStringB[] =
+    "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
 
 constexpr char kAtomicPrefPath[] = "path1";
 constexpr char kSplitPrefPath[] = "extension";
@@ -114,4 +117,4 @@ TEST_F(RegistryHashStoreContentsWinTest, TestReset) {
   split_macs.clear();
   EXPECT_FALSE(contents->GetSplitMacs(kSplitPrefPath, &split_macs));
   EXPECT_EQ(0U, split_macs.size());
-}
+}