Support tasks injection into a running VM.

test/cctest/test-debug.cc

Index: test/cctest/test-debug.cc
diff --git a/test/cctest/test-debug.cc b/test/cctest/test-debug.cc
index c3c65fd2f0256113f9594b29681ce2e136e0a76a..fa2a24b10370a9ed187862173cf5bbe8520a8016 100644
--- a/test/cctest/test-debug.cc
+++ b/test/cctest/test-debug.cc
@@ -7396,6 +7396,49 @@ TEST(DebuggerCreatesContextIffActive) {
 }
 
 
+class DelayedTask : public v8::base::Thread {
+ public:
+  DelayedTask(v8::Isolate* isolate, v8::Debug::Task* task, int delay_ms)
+      : Thread(Options("DelayedTask")),
+        isolate_(isolate),
+        task_(task),
+        delay_ms_(delay_ms) {}
+  void Run() override {
+    v8::base::OS::Sleep(delay_ms_);

[yurys, 2014/12/17 14:25:03]

We can avoid this Sleep. E.g. "while" loop below can call a native function that
would on first call start this thread and after that would return false until
StopExecutionTask is executed and flips some flag.

[alph, 2014/12/17 15:05:46]

I would like to make sure the BreakAndRun is engaged when the VM loops in a pure
JS code (i.e. having no native callbacks).
I realize Sleep does not guarantee that, but it makes the signal fall into
random points of VM execution, i.e. it covers more cases. The test should not
fail in any case, so it is not a source of flakiness.

+    v8::Debug::BreakAndRun(isolate_, task_);

[yurys, 2014/12/17 14:25:03]

task_ = NULL?

[alph, 2014/12/17 15:05:46]

Done.

+  }
+
+ private:
+  v8::Isolate* isolate_;
+  v8::Debug::Task* task_;
+  int delay_ms_;
+};
+
+
+class StopExecutionTask : public v8::Debug::Task {
+ public:
+  explicit StopExecutionTask(LocalContext& context) : context_(context) {}
+  void Run() override {
+    context_->Global()->Set(v8_str("stop"), v8::True(context_->GetIsolate()));

[yurys, 2014/12/17 14:25:03]

We can use a static C++ variable instead, it would indicate that we can break
the loop.

[alph, 2014/12/17 15:05:46]

See my comment above. I'd like it to be a pure JS loop.

+  }
+
+ private:
+  LocalContext& context_;
+};
+
+
+TEST(RunTaskWhileLooping) {
+  LocalContext env;
+  v8::HandleScope scope(env->GetIsolate());
+
+  v8::Debug::Task* task = new StopExecutionTask(env);
+  DelayedTask delayed_task(env->GetIsolate(), task, 100);

[yurys, 2014/12/17 14:25:03]

Or can we at least reduce the delay to 10 or something?

[alph, 2014/12/17 15:05:46]

Acknowledged.

+  CompileRun("var stop = false;");
+  delayed_task.Start();
+  CompileRun("while (!stop) {}");
+}
+
+
 TEST(LiveEditEnabled) {
   v8::internal::FLAG_allow_natives_syntax = true;
   LocalContext env;