[inspector] doesn't run user code to stringify console method arg

Otherwise user code can produce an exception and we will crash.

R=jakob@chromium.org

Bug: chromium:736302
Change-Id: I078150909b0348a63e8c375b508e34fc4751b4ab
Reviewed-on: https://chromium-review.googlesource.com/565628
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46566}

src/inspector/v8-console.cc

@@ -112,6 +112,10 @@ class ConsoleHelper {
   String16 firstArgToString(const String16& defaultValue) {
     if (m_info.Length() < 1) return defaultValue;
     v8::Local<v8::String> titleValue;
+    v8::TryCatch tryCatch(m_context->GetIsolate());
+    v8::Isolate::DisallowJavascriptExecutionScope throwJs(
+        m_context->GetIsolate(),
+        v8::Isolate::DisallowJavascriptExecutionScope::THROW_ON_FAILURE);
     if (m_info[0]->IsObject()) {
       if (!m_info[0].As<v8::Object>()->ObjectProtoToString(m_context).ToLocal(
               &titleValue))

test/inspector/runtime/regression-736302-expected.txt

+crbug.com/736302
+{
+    method : Runtime.consoleAPICalled
+    params : {
+        args : [
+            [0] : {
+                type : string
+                value : 1
+            }
+        ]
+        executionContextId : <executionContextId>
+        stackTrace : {
+            callFrames : [
+                [0] : {
+                    columnNumber : 10
+                    functionName : 
+                    lineNumber : 1
+                    scriptId : <scriptId>
+                    url : 
+                }
+            ]
+        }
+        timestamp : <timestamp>
+        type : count
+    }
+}
+{
+    type : undefined
+}

test/inspector/runtime/regression-736302.js

+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+let {session, contextGroup, Protocol} = InspectorTest.start('crbug.com/736302');
+
+(async function main() {
+  Protocol.Runtime.enable();
+  Protocol.Runtime.onConsoleAPICalled(InspectorTest.logMessage);
+  let r = await Protocol.Runtime.evaluate({expression: `
+  console.count({
+    get [Symbol.toStringTag]() {
+      throw new Error();
+    }
+  });`});
+  InspectorTest.logMessage(r.result.result);
+  InspectorTest.completeTest();
+})();