Make exception thrown via v8 public API propagate to v8::TryCatch as JS thrown exceptions do.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 13ffc1353b4bd34b94526686ec1b34c7ef2f64ca..61f180ea244b4a906c01ea78ae4695dca528a532 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -187,6 +187,9 @@ class ThreadLocalTop BASE_EMBEDDED {
   // unify them later.
   MaybeObject* scheduled_exception_;
   bool external_caught_exception_;
+  // True if unhandled message is being currently reported by
+  // MessageHandler::ReportMessage.
+  bool in_exception_reporting_;
   SaveContext* save_context_;
   v8::TryCatch* catcher_;
 
@@ -490,6 +493,9 @@ class Isolate {
   bool external_caught_exception() {
     return thread_local_top_.external_caught_exception_;
   }
+  void set_external_caught_exception(bool value) {
+    thread_local_top_.external_caught_exception_ = value;
+  }
   void set_pending_exception(MaybeObject* exception) {
     thread_local_top_.pending_exception_ = exception;
   }
@@ -517,6 +523,18 @@ class Isolate {
   bool* external_caught_exception_address() {
     return &thread_local_top_.external_caught_exception_;
   }
+  bool in_exception_reporting() {
+    return thread_local_top_.in_exception_reporting_;
+  }
+  void set_in_exception_reporting(bool value) {
+    thread_local_top_.in_exception_reporting_ = value;
+  }
+  v8::TryCatch* catcher() {
+    return thread_local_top_.catcher_;
+  }
+  void set_catcher(v8::TryCatch* catcher) {
+    thread_local_top_.catcher_ = catcher;
+  }
 
   MaybeObject** scheduled_exception_address() {
     return &thread_local_top_.scheduled_exception_;
@@ -587,6 +605,27 @@ class Isolate {
   // JavaScript code.  If an exception is scheduled true is returned.
   bool OptionalRescheduleException(bool is_bottom_call);
 
+  class ExceptionScope {
+   public:
+    explicit ExceptionScope(Isolate* isolate) :
+      // Scope currently can only be used for regular exceptions, not
+      // failures like OOM or termination exception.
+      isolate_(isolate),
+      pending_exception_(isolate_->pending_exception()->ToObjectUnchecked()),
+      catcher_(isolate_->catcher())
+    { }
+
+    ~ExceptionScope() {
+      isolate_->set_catcher(catcher_);
+      isolate_->set_pending_exception(*pending_exception_);
+    }
+
+   private:
+    Isolate* isolate_;
+    Handle<Object> pending_exception_;
+    v8::TryCatch* catcher_;
+  };
+
   void SetCaptureStackTraceForUncaughtExceptions(
       bool capture,
       int frame_limit,
@@ -1015,6 +1054,8 @@ class Isolate {
 
   void FillCache();
 
+  void PropagatePendingExceptionToExternalTryCatch();
+
   int stack_trace_nesting_level_;
   StringStream* incomplete_message_;
   // The preallocated memory thread singleton.