Fix: console message only has the 1st argument

Bug: chromium:967927
Change-Id: Id84f8ebd1ecbad1b3d1fc41ec5d35a497e1ce506
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1649174
Commit-Queue: Harley Li <hhli@chromium.org>
Reviewed-by: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62396}

src/inspector/string-16.h

@@ -96,6 +96,10 @@ class String16 {
   inline String16 operator+(const String16& other) const {
     return String16(m_impl + other.m_impl);
   }
+  inline String16& operator+=(const String16& other) {
+    m_impl += other.m_impl;
+    return *this;
+  }
 
   // Defined later, since it uses the String16Builder.
   template <typename... T>

src/inspector/v8-console-message.cc

@@ -427,9 +427,11 @@ std::unique_ptr<V8ConsoleMessage> V8ConsoleMessage::createForConsoleAPI(
     message->m_v8Size +=
         v8::debug::EstimatedValueSize(isolate, arguments.at(i));
   }
-  if (arguments.size())
-    message->m_message =
-        V8ValueStringBuilder::toString(arguments[0], v8Context);
+  for (size_t i = 0, num_args = arguments.size(); i < num_args; ++i) {
+    if (i) message->m_message += String16(" ");
+    message->m_message +=
+        V8ValueStringBuilder::toString(arguments[i], v8Context);
+  }
 
   v8::Isolate::MessageErrorLevel clientLevel = v8::Isolate::kMessageInfo;
   if (type == ConsoleAPIType::kDebug || type == ConsoleAPIType::kCount ||