Fix UnguessableToken::ToString()

Make sure that ToString() would produce distinct strings for
distinct tokens.

Bug: 815217
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel
Change-Id: I38ea5bfad061610e95945eb31187cb3c02f737cf
Reviewed-on: https://chromium-review.googlesource.com/934824Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Elad Alon <eladalon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539115}

base/unguessable_token.cc

@@ -14,7 +14,7 @@ UnguessableToken::UnguessableToken(uint64_t high, uint64_t low)
     : high_(high), low_(low) {}
 
 std::string UnguessableToken::ToString() const {
-  return base::StringPrintf("%08" PRIX64 "%08" PRIX64, high_, low_);
+  return base::StringPrintf("%016" PRIX64 "%016" PRIX64, high_, low_);
 }
 
 // static

base/unguessable_token_unittest.cc

@@ -78,18 +78,41 @@ TEST(UnguessableTokenTest, VerifyValueSerialization) {
   EXPECT_EQ(token, deserialized);
 }
 
-TEST(UnguessableTokenTest, VerifyToString) {
+// Common case (~88% of the time) - no leading zeroes in high_ nor low_.
+TEST(UnguessableTokenTest, VerifyToString1) {
+  UnguessableToken token =
+      UnguessableToken::Deserialize(0x1234567890ABCDEF, 0xFEDCBA0987654321);
+  std::string expected = "1234567890ABCDEFFEDCBA0987654321";
+
+  EXPECT_EQ(expected, token.ToString());
+
+  std::string expected_stream = "(1234567890ABCDEFFEDCBA0987654321)";
+  std::stringstream stream;
+  stream << token;
+  EXPECT_EQ(expected_stream, stream.str());
+}
+
+// Less common case - leading zeroes in high_ or low_ (testing with both).
+TEST(UnguessableTokenTest, VerifyToString2) {
   UnguessableToken token = UnguessableToken::Deserialize(0x123, 0xABC);
-  std::string expected = "0000012300000ABC";
+  std::string expected = "00000000000001230000000000000ABC";
 
   EXPECT_EQ(expected, token.ToString());
 
-  std::string expected_stream = "(0000012300000ABC)";
+  std::string expected_stream = "(00000000000001230000000000000ABC)";
   std::stringstream stream;
   stream << token;
   EXPECT_EQ(expected_stream, stream.str());
 }
 
+TEST(UnguessableTokenTest, VerifyToStringUniqueness) {
+  const UnguessableToken token1 =
+      UnguessableToken::Deserialize(0x0000000012345678, 0x0000000123456789);
+  const UnguessableToken token2 =
+      UnguessableToken::Deserialize(0x0000000123456781, 0x0000000023456789);
+  EXPECT_NE(token1.ToString(), token2.ToString());
+}
+
 TEST(UnguessableTokenTest, VerifySmallerThanOperator) {
   // Deserialize is used for testing purposes.
   // Use UnguessableToken::Create() in production code instead.

components/viz/common/surfaces/local_surface_id_unittest.cc

@@ -22,16 +22,19 @@ TEST(LocalSurfaceIdTest, VerifyToString) {
   const viz::LocalSurfaceId small_local_surface_id(11, 22, small_token);
 
   const std::string verbose_expected =
-      "LocalSurfaceId(11, 22, 0011111100000000)";
-  const std::string brief_expected = "LocalSurfaceId(11, 22, 0011...)";
+      "LocalSurfaceId(11, 22, " + token.ToString() + ")";
+  const std::string brief_expected =
+      "LocalSurfaceId(11, 22, " + token.ToString().substr(0, 4) + "...)";
 
   const std::string big_verbose_expected =
-      "LocalSurfaceId(11, 22, 123456789ABCABCABC)";
-  const std::string big_brief_expected = "LocalSurfaceId(11, 22, 1234...)";
+      "LocalSurfaceId(11, 22, " + big_token.ToString() + ")";
+  const std::string big_brief_expected =
+      "LocalSurfaceId(11, 22, " + big_token.ToString().substr(0, 4) + "...)";
 
   const std::string small_verbose_expected =
-      "LocalSurfaceId(11, 22, 0000000000000001)";
-  const std::string small_brief_expected = "LocalSurfaceId(11, 22, 0000...)";
+      "LocalSurfaceId(11, 22, " + small_token.ToString() + ")";
+  const std::string small_brief_expected =
+      "LocalSurfaceId(11, 22, " + small_token.ToString().substr(0, 4) + "...)";
 
   int previous_log_lvl = logging::GetMinLogLevel();