Fixes shutdown crashes.

- Restores fix to debug message queue.
- Fixes for precompilation.

BUG=
R=johnmccutchan@google.com, rmacnak@google.com

Review URL: https://codereview.chromium.org/1406013004 .

runtime/vm/debugger.cc

@@ -1277,6 +1277,12 @@ Debugger::~Debugger() {
 
 
 void Debugger::Shutdown() {
+  // TODO(johnmccutchan): Do not create a debugger for isolates that don't need
+  // them. Then, assert here that isolate_ is not one of those isolates.
+  if ((isolate_ == Dart::vm_isolate()) ||
+      ServiceIsolate::IsServiceIsolateDescendant(isolate_)) {
+    return;
+  }
   while (breakpoint_locations_ != NULL) {
     BreakpointLocation* bpt = breakpoint_locations_;
     breakpoint_locations_ = breakpoint_locations_->next();
@@ -1294,9 +1300,7 @@ void Debugger::Shutdown() {
     delete bpt;
   }
   // Signal isolate shutdown event.
-  if (!ServiceIsolate::IsServiceIsolateDescendant(isolate_)) {
-    SignalIsolateEvent(DebuggerEvent::kIsolateShutdown);
-  }
+  SignalIsolateEvent(DebuggerEvent::kIsolateShutdown);
 }
 
 

runtime/vm/service_isolate.cc

@@ -319,6 +319,7 @@ class RunServiceTask : public ThreadPool::Task {
                                                    &error));
     if (isolate == NULL) {
       OS::PrintErr("vm-service: Isolate creation error: %s\n", error);
+      ServiceIsolate::SetServiceIsolate(NULL);
       ServiceIsolate::FinishedInitializing();
       return;
     }

runtime/vm/virtual_memory.cc

@@ -33,7 +33,9 @@ VirtualMemory* VirtualMemory::ForInstructionsSnapshot(void* pointer,
   // Memory for precompilated instructions was allocated by the embedder, so
   // create a VirtualMemory without allocating.
   MemoryRegion region(pointer, size);
-  return new VirtualMemory(region);
+  VirtualMemory* memory = new VirtualMemory(region);
+  memory->embedder_allocated_ = true;
+  return memory;
 }
 
 }  // namespace dart

runtime/vm/virtual_memory.h

@@ -69,6 +69,8 @@ class VirtualMemory {
   // Commit a reserved memory area, so that the memory can be accessed.
   bool Commit(uword addr, intptr_t size, bool is_executable);
 
+  bool embedder_allocated() const { return embedder_allocated_; }
+
   static VirtualMemory* ForInstructionsSnapshot(void* pointer, uword size);
 
  private:
@@ -92,6 +94,9 @@ class VirtualMemory {
 
   static uword page_size_;
 
+  // True for a region provided by the embedder.
+  bool embedder_allocated_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(VirtualMemory);
 };
 

runtime/vm/virtual_memory_android.cc

@@ -53,7 +53,9 @@ static void unmap(void* address, intptr_t size) {
 
 
 VirtualMemory::~VirtualMemory() {
-  unmap(address(), reserved_size_);
+  if (!embedder_allocated()) {
+    unmap(address(), reserved_size_);
+  }
 }
 
 

runtime/vm/virtual_memory_linux.cc

@@ -52,7 +52,9 @@ static void unmap(void* address, intptr_t size) {
 
 
 VirtualMemory::~VirtualMemory() {
-  unmap(address(), reserved_size_);
+  if (!embedder_allocated()) {
+    unmap(address(), reserved_size_);
+  }
 }
 
 

runtime/vm/virtual_memory_macos.cc

@@ -53,7 +53,9 @@ static void unmap(void* address, intptr_t size) {
 
 
 VirtualMemory::~VirtualMemory() {
-  unmap(address(), reserved_size_);
+  if (!embedder_allocated()) {
+    unmap(address(), reserved_size_);
+  }
 }
 
 

runtime/vm/virtual_memory_win.cc

@@ -33,7 +33,7 @@ VirtualMemory* VirtualMemory::ReserveInternal(intptr_t size) {
 
 
 VirtualMemory::~VirtualMemory() {
-  if (reserved_size_ == 0) {
+  if (embedder_allocated() || (reserved_size_ == 0)) {
     return;
   }
   if (VirtualFree(address(), 0, MEM_RELEASE) == 0) {