Add necessary support functions so that embedders can implemented pause on start and exit

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 
 #include "platform/assert.h"
 #include "lib/stacktrace.h"
@@ skipping 1347 matching lines @@
 
 DART_EXPORT void Dart_ThreadEnableProfiling() {
   OSThread* os_thread = OSThread::Current();
   if (os_thread == NULL) {
     return;
   }
   os_thread->EnableThreadInterrupts();
 }
 
 
+DART_EXPORT bool Dart_ShouldPauseOnStart() {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  return isolate->message_handler()->pause_on_start();
+}
+
+
+DART_EXPORT void Dart_SetShouldPauseOnStart(bool v) {

[turnidge, 2016/02/03 21:33:36]

v -> value or perhaps should_pause.

[Cutch, 2016/02/03 23:04:04]

Done.

+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  isolate->set_pause_isolates_flags_overridden(true);
+  return isolate->message_handler()->set_pause_on_start(v);
+}
+
+
+DART_EXPORT bool Dart_IsPausedOnStart() {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  return isolate->message_handler()->paused_on_start();
+}
+
+
+DART_EXPORT void Dart_SetPausedOnStart(bool v) {

[turnidge, 2016/02/03 21:33:36]

v -> value or paused, here and below.

[Cutch, 2016/02/03 23:04:04]

Done.

+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  if (isolate->message_handler()->paused_on_start() != v) {
+    isolate->message_handler()->PausedOnStart(v);
+    if (v) {
+      isolate->message_handler()->NotifyPauseOnStart();
+    }
+  }

[turnidge, 2016/02/03 21:33:36]

As discussed offline, consider making a single api entry point
(SetPausedOnStart) instead of the current two public ones (PausedOnStart,
NotifyPauseOnStart).

[Cutch, 2016/02/03 23:04:04]

Done.

+}
+
+
+DART_EXPORT bool Dart_ShouldPauseOnExit() {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  return isolate->message_handler()->pause_on_exit();
+}
+
+
+DART_EXPORT void Dart_SetShouldPauseOnExit(bool v) {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  isolate->set_pause_isolates_flags_overridden(true);
+  return isolate->message_handler()->set_pause_on_exit(v);
+}
+
+
+DART_EXPORT bool Dart_IsPausedOnExit() {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  return isolate->message_handler()->paused_on_exit();
+}
+
+
+DART_EXPORT void Dart_SetPausedOnExit(bool v) {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  if (isolate->message_handler()->paused_on_exit() != v) {
+    isolate->message_handler()->PausedOnExit(v);
+    if (v) {
+      isolate->message_handler()->NotifyPauseOnExit();
+    }
+  }
+}
+
+
 DART_EXPORT void Dart_ExitIsolate() {
   Thread* T = Thread::Current();
   CHECK_ISOLATE(T->isolate());
   // The Thread structure is disassociated from the isolate, we do the
   // safepoint transition explicity here instead of using the TransitionXXX
   // scope objects as the original transition happened outside this scope in
   // Dart_EnterIsolate/Dart_CreateIsolate.
   ASSERT(T->execution_state() == Thread::kThreadInNative);
   T->ExitSafepoint();
   T->set_execution_state(Thread::kThreadInVM);
@@ skipping 194 matching lines @@
   TransitionNativeToVM transition(T);
   if (I->message_handler()->HandleNextMessage() != MessageHandler::kOK) {
     Dart_Handle error = Api::NewHandle(T, I->object_store()->sticky_error());
     I->object_store()->clear_sticky_error();
     return error;
   }
   return Api::Success();
 }
 
 
+DART_EXPORT Dart_Handle Dart_HandleMessages() {
+  Thread* T = Thread::Current();
+  Isolate* I = T->isolate();
+  CHECK_API_SCOPE(T);
+  CHECK_CALLBACK_STATE(T);
+  API_TIMELINE_BEGIN_END;
+  TransitionNativeToVM transition(T);
+  if (I->message_handler()->HandleNormalMessages() != MessageHandler::kOK) {
+    Dart_Handle error = Api::NewHandle(T, I->object_store()->sticky_error());
+    I->object_store()->clear_sticky_error();
+    return error;
+  }
+  return Api::Success();
+}
+
+
 DART_EXPORT bool Dart_HandleServiceMessages() {
   Thread* T = Thread::Current();
   Isolate* I = T->isolate();
   CHECK_API_SCOPE(T);
   CHECK_CALLBACK_STATE(T);
   API_TIMELINE_DURATION;
   TransitionNativeToVM transition(T);
   ASSERT(I->GetAndClearResumeRequest() == false);
   MessageHandler::MessageStatus status =
       I->message_handler()->HandleOOBMessages();
@@ skipping 4423 matching lines @@
   return Api::Success();
 }
 #endif  // DART_PRECOMPILER
 
 
 DART_EXPORT bool Dart_IsRunningPrecompiledCode() {
   return Dart::IsRunningPrecompiledCode();
 }
 
 }  // namespace dart