[inspector] Add some context scopes to inspector code

Currently, the external API (e.g. v8::Object::Get()) will enter the
context passed to it automatically. This is incorrect and causes some
trouble for Blink, so we want to change that.

It then becomes a potential problem to call the external API without
first entering a context, which the inspector code does in some
places. This patch aims to correct this.

BUG=v8:6307

Review-Url: https://codereview.chromium.org/2841053002
Cr-Commit-Position: refs/heads/master@{#44917}

src/inspector/v8-function-call.cc

@@ -75,6 +75,8 @@ v8::Local<v8::Value> V8FunctionCall::call(bool& hadException,
 }
 
 v8::Local<v8::Value> V8FunctionCall::callWithoutExceptionHandling() {
+  v8::Context::Scope contextScope(m_context);
+
   v8::Local<v8::Object> thisObject = v8::Local<v8::Object>::Cast(m_value);
   v8::Local<v8::Value> value;
   if (!thisObject->Get(m_context, m_name).ToLocal(&value))

src/inspector/v8-regex.cc

@@ -49,6 +49,7 @@ int V8Regex::match(const String16& string, int startFrom,
   v8::Isolate* isolate = m_inspector->isolate();
   v8::HandleScope handleScope(isolate);
   v8::Local<v8::Context> context = m_inspector->regexContext();
+  v8::Context::Scope contextScope(context);
   v8::MicrotasksScope microtasks(isolate,
                                  v8::MicrotasksScope::kDoNotRunMicrotasks);
   v8::TryCatch tryCatch(isolate);