Use |nullptr| instead of |NULL| in crc32_unittest.cc

https://google.github.io/styleguide/cppguide.html#0_and_nullptr/NULL
says:
"For pointers (address values), use nullptr, as this provides
type-safety."

Furthermore, NULL/0 won't compile if we change |SomeClass*| to
|CheckedPtr<SomeClass>|. See go/miracleptr for project details.

Bug: 1080832
Change-Id: I00908679918e2c2316b25d9fd834914e540bd163
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2512484
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Auto-Submit: Bartek Nowierski <bartekn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822946}

rlz/lib/crc32_unittest.cc

@@ -16,11 +16,11 @@ TEST(Crc32Unittest, ByteTest) {
     // Externally calculated at http://crc32-checksum.waraxe.us/
     int crc;
   } kData[] = {
-    {"Hello"           ,  5, 0xF7D18982},
-    {"Google"          ,  6, 0x62B0F067},
-    {""                ,  0, 0x0},
-    {"One more string.", 16, 0x0CA14970},
-    {NULL              ,  0, 0x0},
+      {"Hello", 5, 0xF7D18982},
+      {"Google", 6, 0x62B0F067},
+      {"", 0, 0x0},
+      {"One more string.", 16, 0x0CA14970},
+      {nullptr, 0, 0x0},
   };
 
   for (int i = 0; kData[i].data; i++)
@@ -35,12 +35,12 @@ TEST(Crc32Unittest, CharTest) {
     // Externally calculated at http://crc32-checksum.waraxe.us/
     int crc;
   } kData[] = {
-    {"Hello"           , 0xF7D18982},
-    {"Google"          , 0x62B0F067},
-    {""                , 0x0},
-    {"One more string.", 0x0CA14970},
-    {"Google\r\n"      , 0x83A3E860},
-    {NULL              , 0x0},
+      {"Hello", 0xF7D18982},
+      {"Google", 0x62B0F067},
+      {"", 0x0},
+      {"One more string.", 0x0CA14970},
+      {"Google\r\n", 0x83A3E860},
+      {nullptr, 0x0},
   };
 
   int crc;