diff --git a/src/inspector/string-util.h b/src/inspector/string-util.h
index c484aab2ed..1936c11d00 100644
--- a/src/inspector/string-util.h
+++ b/src/inspector/string-util.h
@@ -33,9 +33,21 @@ class StringUtil {
   }
   static String fromDouble(double number) { return String::fromDouble(number); }
   static const size_t kNotFound = String::kNotFound;
+  static void builderAppend(StringBuilder& builder, const String& s) {
+    builder.append(s);
+  }
+  static void builderAppend(StringBuilder& builder, UChar c) {
+    builder.append(c);
+  }
+  static void builderAppend(StringBuilder& builder, const char* s, size_t len) {
+    builder.append(s, len);
+  }
   static void builderReserve(StringBuilder& builder, size_t capacity) {
     builder.reserveCapacity(capacity);
   }
+  static String builderToString(StringBuilder& builder) {
+    return builder.toString();
+  }
   static std::unique_ptr<protocol::Value> parseJSON(const String16& json);
   static std::unique_ptr<protocol::Value> parseJSON(const StringView& json);
 };
diff --git a/third_party/inspector_protocol/README.v8 b/third_party/inspector_protocol/README.v8
index 178a1a75e3..68421ea189 100644
--- a/third_party/inspector_protocol/README.v8
+++ b/third_party/inspector_protocol/README.v8
@@ -2,7 +2,7 @@ Name: inspector protocol
 Short Name: inspector_protocol
 URL: https://chromium.googlesource.com/deps/inspector_protocol/
 Version: 0
-Revision: 715b83a3cfb45ce6c67b6c6fdd2c16391b5db896
+Revision: 1a131872167f0f7653629326891aa3ec94417f27
 License: BSD
 License File: LICENSE
 Security Critical: no
diff --git a/third_party/inspector_protocol/lib/ErrorSupport_cpp.template b/third_party/inspector_protocol/lib/ErrorSupport_cpp.template
index e4ae0c4e47..2108262a12 100644
--- a/third_party/inspector_protocol/lib/ErrorSupport_cpp.template
+++ b/third_party/inspector_protocol/lib/ErrorSupport_cpp.template
@@ -32,12 +32,12 @@ void ErrorSupport::addError(const String& error)
     StringBuilder builder;
     for (size_t i = 0; i < m_path.size(); ++i) {
         if (i)
-            builder.append('.');
-        builder.append(m_path[i]);
+            StringUtil::builderAppend(builder, '.');
+        StringUtil::builderAppend(builder, m_path[i]);
     }
-    builder.append(": ");
-    builder.append(error);
-    m_errors.push_back(builder.toString());
+    StringUtil::builderAppend(builder, ": ");
+    StringUtil::builderAppend(builder, error);
+    m_errors.push_back(StringUtil::builderToString(builder));
 }
 
 bool ErrorSupport::hasErrors()
@@ -50,10 +50,10 @@ String ErrorSupport::errors()
     StringBuilder builder;
     for (size_t i = 0; i < m_errors.size(); ++i) {
         if (i)
-            builder.append("; ");
-        builder.append(m_errors[i]);
+            StringUtil::builderAppend(builder, "; ");
+        StringUtil::builderAppend(builder, m_errors[i]);
     }
-    return builder.toString();
+    return StringUtil::builderToString(builder);
 }
 
 {% for namespace in config.protocol.namespace %}
diff --git a/third_party/inspector_protocol/lib/Parser_cpp.template b/third_party/inspector_protocol/lib/Parser_cpp.template
index 11a60639df..4bf6bebc46 100644
--- a/third_party/inspector_protocol/lib/Parser_cpp.template
+++ b/third_party/inspector_protocol/lib/Parser_cpp.template
@@ -337,7 +337,7 @@ bool decodeString(const Char* start, const Char* end, StringBuilder* output)
     while (start < end) {
         uint16_t c = *start++;
         if ('\\' != c) {
-            output->append(c);
+            StringUtil::builderAppend(*output, c);
             continue;
         }
 	if (start == end)
@@ -382,7 +382,7 @@ bool decodeString(const Char* start, const Char* end, StringBuilder* output)
         default:
             return false;
         }
-        output->append(c);
+        StringUtil::builderAppend(*output, c);
     }
     return true;
 }
@@ -400,7 +400,7 @@ bool decodeString(const Char* start, const Char* end, String* output)
     StringUtil::builderReserve(buffer, end - start);
     if (!decodeString(start, end, &buffer))
         return false;
-    *output = buffer.toString();
+    *output = StringUtil::builderToString(buffer);
     return true;
 }
 
diff --git a/third_party/inspector_protocol/lib/Values_cpp.template b/third_party/inspector_protocol/lib/Values_cpp.template
index 8fe128ef48..6f8b14c16c 100644
--- a/third_party/inspector_protocol/lib/Values_cpp.template
+++ b/third_party/inspector_protocol/lib/Values_cpp.template
@@ -17,13 +17,13 @@ const char* const falseValueString = "false";
 inline bool escapeChar(uint16_t c, StringBuilder* dst)
 {
     switch (c) {
-    case '\b': dst->append("\\b"); break;
-    case '\f': dst->append("\\f"); break;
-    case '\n': dst->append("\\n"); break;
-    case '\r': dst->append("\\r"); break;
-    case '\t': dst->append("\\t"); break;
-    case '\\': dst->append("\\\\"); break;
-    case '"': dst->append("\\\""); break;
+    case '\b': StringUtil::builderAppend(*dst, "\\b"); break;
+    case '\f': StringUtil::builderAppend(*dst, "\\f"); break;
+    case '\n': StringUtil::builderAppend(*dst, "\\n"); break;
+    case '\r': StringUtil::builderAppend(*dst, "\\r"); break;
+    case '\t': StringUtil::builderAppend(*dst, "\\t"); break;
+    case '\\': StringUtil::builderAppend(*dst, "\\\\"); break;
+    case '"': StringUtil::builderAppend(*dst, "\\\""); break;
     default:
         return false;
     }
@@ -34,10 +34,10 @@ const char hexDigits[17] = "0123456789ABCDEF";
 
 void appendUnsignedAsHex(uint16_t number, StringBuilder* dst)
 {
-    dst->append("\\u");
+    StringUtil::builderAppend(*dst, "\\u");
     for (size_t i = 0; i < 4; ++i) {
         uint16_t c = hexDigits[(number & 0xF000) >> 12];
-        dst->append(c);
+        StringUtil::builderAppend(*dst, c);
         number <<= 4;
     }
 }
@@ -53,7 +53,7 @@ void escapeStringForJSON(const String& str, StringBuilder* dst)
                 //    is also optional. It would also be a pain to implement here.
                 appendUnsignedAsHex(c, dst);
             } else {
-                dst->append(c);
+                StringUtil::builderAppend(*dst, c);
             }
         }
     }
@@ -61,9 +61,9 @@ void escapeStringForJSON(const String& str, StringBuilder* dst)
 
 void doubleQuoteStringForJSON(const String& str, StringBuilder* dst)
 {
-    dst->append('"');
+    StringUtil::builderAppend(*dst, '"');
     escapeStringForJSON(str, dst);
-    dst->append('"');
+    StringUtil::builderAppend(*dst, '"');
 }
 
 } // anonymous namespace
@@ -96,7 +96,7 @@ bool Value::asSerialized(String*) const
 void Value::writeJSON(StringBuilder* output) const
 {
     DCHECK(m_type == TypeNull);
-    output->append(nullValueString, 4);
+    StringUtil::builderAppend(*output, nullValueString, 4);
 }
 
 std::unique_ptr<Value> Value::clone() const
@@ -109,7 +109,7 @@ String Value::serialize()
     StringBuilder result;
     StringUtil::builderReserve(result, 512);
     writeJSON(&result);
-    return result.toString();
+    return StringUtil::builderToString(result);
 }
 
 bool FundamentalValue::asBoolean(bool* output) const
@@ -146,17 +146,17 @@ void FundamentalValue::writeJSON(StringBuilder* output) const
     DCHECK(type() == TypeBoolean || type() == TypeInteger || type() == TypeDouble);
     if (type() == TypeBoolean) {
         if (m_boolValue)
-            output->append(trueValueString, 4);
+            StringUtil::builderAppend(*output, trueValueString, 4);
         else
-            output->append(falseValueString, 5);
+            StringUtil::builderAppend(*output, falseValueString, 5);
     } else if (type() == TypeDouble) {
         if (!std::isfinite(m_doubleValue)) {
-            output->append(nullValueString, 4);
+            StringUtil::builderAppend(*output, nullValueString, 4);
             return;
         }
-        output->append(StringUtil::fromDouble(m_doubleValue));
+        StringUtil::builderAppend(*output, StringUtil::fromDouble(m_doubleValue));
     } else if (type() == TypeInteger) {
-        output->append(StringUtil::fromInteger(m_integerValue));
+        StringUtil::builderAppend(*output, StringUtil::fromInteger(m_integerValue));
     }
 }
 
@@ -198,7 +198,7 @@ bool SerializedValue::asSerialized(String* output) const
 void SerializedValue::writeJSON(StringBuilder* output) const
 {
     DCHECK(type() == TypeSerialized);
-    output->append(m_serializedValue);
+    StringUtil::builderAppend(*output, m_serializedValue);
 }
 
 std::unique_ptr<Value> SerializedValue::clone() const
@@ -330,17 +330,17 @@ void DictionaryValue::remove(const String& name)
 
 void DictionaryValue::writeJSON(StringBuilder* output) const
 {
-    output->append('{');
+    StringUtil::builderAppend(*output, '{');
     for (size_t i = 0; i < m_order.size(); ++i) {
         Dictionary::const_iterator it = m_data.find(m_order[i]);
         CHECK(it != m_data.end());
         if (i)
-            output->append(',');
+            StringUtil::builderAppend(*output, ',');
         doubleQuoteStringForJSON(it->first, output);
-        output->append(':');
+        StringUtil::builderAppend(*output, ':');
         it->second->writeJSON(output);
     }
-    output->append('}');
+    StringUtil::builderAppend(*output, '}');
 }
 
 std::unique_ptr<Value> DictionaryValue::clone() const
@@ -366,15 +366,15 @@ ListValue::~ListValue()
 
 void ListValue::writeJSON(StringBuilder* output) const
 {
-    output->append('[');
+    StringUtil::builderAppend(*output, '[');
     bool first = true;
     for (const std::unique_ptr<protocol::Value>& value : m_data) {
         if (!first)
-            output->append(',');
+            StringUtil::builderAppend(*output, ',');
         value->writeJSON(output);
         first = false;
     }
-    output->append(']');
+    StringUtil::builderAppend(*output, ']');
 }
 
 std::unique_ptr<Value> ListValue::clone() const