[tracing] Escape UTF8 strings in JSON compliant form.

JSON format does not support \xNN encoding. Use \uNNNN instead.

+ Add myself to the src/tracing/OWNERS

BUG=chromium:895974

Change-Id: I410a09d44af08b61837579fa09d263d897b9385e
Reviewed-on: https://chromium-review.googlesource.com/c/1303535Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57180}

src/tracing/OWNER

+alph@chromium.org

src/tracing/traced-value.cc

@@ -29,12 +29,21 @@ void EscapeAndAppendString(const char* value, std::string* result) {
   while (*value) {
     unsigned char c = *value++;
     switch (c) {
-      case '\t':
-        *result += "\\t";
+      case '\b':
+        *result += "\\b";
+        break;
+      case '\f':
+        *result += "\\f";
         break;
       case '\n':
         *result += "\\n";
         break;
+      case '\r':
+        *result += "\\r";
+        break;
+      case '\t':
+        *result += "\\t";
+        break;
       case '\"':
         *result += "\\\"";
         break;
@@ -44,9 +53,8 @@ void EscapeAndAppendString(const char* value, std::string* result) {
       default:
         if (c < '\x20' || c == '\x7F') {
           char number_buffer[8];
-          base::OS::SNPrintF(
-              number_buffer, arraysize(number_buffer), "\\x%02X",
-              static_cast<unsigned>(static_cast<unsigned char>(c)));
+          base::OS::SNPrintF(number_buffer, arraysize(number_buffer), "\\u%04X",
+                             static_cast<unsigned>(c));
           *result += number_buffer;
         } else {
           *result += c;

test/cctest/test-traced-value.cc

@@ -116,10 +116,11 @@ TEST(Escaping) {
   // Cannot use the expected value literal directly in CHECK_EQ
   // as it fails to process the # character on Windows.
   const char* expected =
-      R"({"a":"abc\"'\\\\x\"y'z\n\t\x17","b":"\x01\x02\x03\x04\x05\x06\x07\x08)"
-      R"(\t\n\x0B\x0C\x0D\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A)"
-      R"(\x1B\x1C\x1D\x1E\x1F !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNO)"
-      R"(PQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F"})";
+      R"({"a":"abc\"'\\\\x\"y'z\n\t\u0017","b":"\u0001\u0002\u0003\u0004\u0005)"
+      R"(\u0006\u0007\b\t\n\u000B\f\r\u000E\u000F\u0010\u0011\u0012\u0013)"
+      R"(\u0014\u0015\u0016\u0017\u0018\u0019\u001A\u001B\u001C\u001D\u001E)"
+      R"(\u001F !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ)"
+      R"([\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\u007F"})";
   CHECK_EQ(expected, json);
 }
 
@@ -129,11 +130,13 @@ TEST(Utf8) {
   auto value = TracedValue::Create();
   value->SetString("a", string1);
   value->SetString("b", string2);
+  // Surrogate pair test. Smile emoji === U+1F601 === \xf0\x9f\x98\x81
+  value->SetString("c", "\U0001F601");
   std::string json;
   value->AppendAsTraceFormat(&json);
   const char* expected =
-      "{\"a\":\"\u041b\u044e\u0431\u043b\u044e \u0442\u0435\u0431\u044f, \u041f"
-      "\u0435\u0442\u0440\u0430 \u0442\u0432\u043e\u0440\u0435\u043d\u044c"
-      "\u0435\",\"b\":\"\u2600\u2600\u26ff\"}";
+      "{\"a\":\"\u041B\u044E\u0431\u043B\u044E \u0442\u0435\u0431\u044F, \u041F"
+      "\u0435\u0442\u0440\u0430 \u0442\u0432\u043E\u0440\u0435\u043D\u044C"
+      "\u0435\",\"b\":\"\u2600\u2600\u26FF\",\"c\":\"\xf0\x9f\x98\x81\"}";
   CHECK_EQ(expected, json);
 }