Revert "Switch profiler from isolates to threads"

runtime/vm/debugger.cc

Index: runtime/vm/debugger.cc
diff --git a/runtime/vm/debugger.cc b/runtime/vm/debugger.cc
index 2c4d54bf04c0bd6dbd76796dab0c00c1fefdd77a..0b3e26139a114c88b0c5c5638e52481a0dbdaf70 100644
--- a/runtime/vm/debugger.cc
+++ b/runtime/vm/debugger.cc
@@ -2515,12 +2515,7 @@ void Debugger::Pause(DebuggerEvent* event) {
   pause_event_->UpdateTimestamp();
   obj_cache_ = new RemoteObjectCache(64);
 
-  // We are about to invoke the debuggers event handler. Disable interrupts
-  // for this thread while waiting for debug commands over the service protocol.
-  {
-    DisableThreadInterruptsScope dtis(Thread::Current());
-    InvokeEventHandler(event);
-  }
+  InvokeEventHandler(event);
 
   pause_event_ = NULL;
   obj_cache_ = NULL;    // Zone allocated
@@ -2561,6 +2556,11 @@ void Debugger::HandleSteppingRequest(DebuggerStackTrace* stack_trace) {
       }
     }
   }
+  if (!isolate_->single_step()) {
+    // We are no longer single stepping, make sure that the ThreadInterrupter
+    // is awake.
+    ThreadInterrupter::WakeUp();
+  }
 }