Refactor isolate interrupts to use OOB messages instead of interrupt bits.

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index fd303176efebd55419cd3663c827405530c3c1f6..7f59321f13e83b0338066adc027559e9602bb455 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -113,6 +113,27 @@ class IsolateVisitor {
 
 class Isolate : public BaseIsolate {
  public:
+  // Keep both these enums in sync with isolate_patch.dart.
+  // The different Isolate API message types.
+  enum LibMsgId {
+    kPauseMsg = 1,
+    kResumeMsg = 2,
+    kPingMsg = 3,
+    kKillMsg = 4,
+    kAddExitMsg = 5,
+    kDelExitMsg = 6,
+    kAddErrorMsg = 7,
+    kDelErrorMsg = 8,
+    kErrorFatalMsg = 9,
+    kInterruptMsg = 10,
+  };
+  // The different Isolate API message priorities for ping and kill messages.
+  enum LibMsgPriority {
+    kImmediateAction = 0,
+    kBeforeNextEventAction = 1,
+    kAsEventAction = 2
+  };
+
   ~Isolate();
 
   static inline Isolate* Current() {
@@ -185,6 +206,8 @@ class Isolate : public BaseIsolate {
   }
   uint64_t terminate_capability() const { return terminate_capability_; }
 
+  void SendInternalLibMessage(LibMsgId msg_id, uint64_t capability);
+
   Heap* heap() const { return heap_; }
   void set_heap(Heap* value) { heap_ = value; }
   static intptr_t heap_offset() { return OFFSET_OF(Isolate, heap_); }
@@ -319,17 +342,14 @@ class Isolate : public BaseIsolate {
 
   // Interrupt bits.
   enum {
-    kApiInterrupt = 0x1,      // An interrupt from Dart_InterruptIsolate.
+    kVMInterrupt = 0x1,  // Internal VM checks: safepoints, store buffers, etc.
     kMessageInterrupt = 0x2,  // An interrupt to process an out of band message.
-    kVMInterrupt = 0x4,  // Internal VM checks: safepoints, store buffers, etc.
 
-    kInterruptsMask =
-        kApiInterrupt |
-        kMessageInterrupt |
-        kVMInterrupt,
+    kInterruptsMask = (kVMInterrupt | kMessageInterrupt),
   };
 
   void ScheduleInterrupts(uword interrupt_bits);
+  RawError* HandleInterrupts();
   uword GetAndClearInterrupts();
 
   // Marks all libraries as loaded.