Add support for interrupting an isolate in the vm. Interrupts are

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
===================================================================
--- runtime/vm/isolate.h	(revision 2528)
+++ runtime/vm/isolate.h	(working copy)
@@ -23,7 +23,7 @@
 class Heap;
 class LongJump;
 class MessageQueue;
-class Monitor;
+class Mutex;
 class ObjectPointerVisitor;
 class ObjectStore;
 class RawContext;
@@ -219,18 +219,30 @@
     library_tag_handler_ = value;
   }
 
-  static void SetCreateCallback(Dart_IsolateCreateCallback cback);
-  static Dart_IsolateCreateCallback CreateCallback();
+  void SetStackLimit(uword value);
+  void SetStackLimitFromCurrentTOS(uword isolate_stack_top);
 
   uword stack_limit_address() const {
     return reinterpret_cast<uword>(&stack_limit_);
   }
 
-  void SetStackLimit(uword value);
+  // The current stack limit.  This may be overwritten with a special
+  // value to trigger interrupts.
   uword stack_limit() const { return stack_limit_; }
 
-  void SetStackLimitFromCurrentTOS(uword isolate_stack_top);
+  // The true stack limit for this isolate.  This does not change
+  // after isolate initialization.
+  uword saved_stack_limit() const { return saved_stack_limit_; }
 
+  enum {
+    kInterruptsMask = 0x1,
+    kApiInterrupt = 0x1,  // An interrupt from Dart_InterruptIsolate.
+    // More interrupt types will go here.
+  };
+
+  void ScheduleInterrupts(uword interrupt_bits);
+  uword GetAndClearInterrupts();
+
   // Returns null on success, unhandled exception on failure.
   RawObject* StandardRunLoop();
 
@@ -239,6 +251,12 @@
 
   Debugger* debugger() const { return debugger_; }
 
+  static void SetCreateCallback(Dart_IsolateCreateCallback cback);
+  static Dart_IsolateCreateCallback CreateCallback();
+
+  static void SetInterruptCallback(Dart_IsolateInterruptCallback cback);
+  static Dart_IsolateInterruptCallback InterruptCallback();
+
  private:
   Isolate();
 
@@ -250,7 +268,6 @@
   static const uword kDefaultStackSize = (1 * MB);
 
   StoreBufferBlock store_buffer_;
-  Monitor* monitor_;
   MessageQueue* message_queue_;
   Dart_PostMessageCallback post_message_callback_;
   Dart_ClosePortCallback close_port_callback_;
@@ -278,10 +295,13 @@
   Debugger* debugger_;
   LongJump* long_jump_base_;
   TimerList timer_list_;
+  intptr_t ast_node_id_;
+  Mutex* mutex_;  // protects stack_limit_ and saved_stack_limit_.
   uword stack_limit_;
-  intptr_t ast_node_id_;
+  uword saved_stack_limit_;
 
   static Dart_IsolateCreateCallback create_callback_;
+  static Dart_IsolateInterruptCallback interrupt_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(Isolate);
 };