Fix crash with OSR after isolate reload.

runtime/vm/code_generator.cc

Index: runtime/vm/code_generator.cc
diff --git a/runtime/vm/code_generator.cc b/runtime/vm/code_generator.cc
index 4b572a7cdf8b9258e0c4fbb0736ca30285d25818..2058619ef4acfb1dfb4714518fb58f9a59bb0af4 100644
--- a/runtime/vm/code_generator.cc
+++ b/runtime/vm/code_generator.cc
@@ -1341,6 +1341,7 @@ DEFINE_RUNTIME_ENTRY(StackOverflow, 0) {
     ASSERT(frame != NULL);
     const Code& code = Code::ZoneHandle(frame->LookupDartCode());
     ASSERT(!code.IsNull());
+    ASSERT(!code.is_optimized());
     const Function& function = Function::Handle(code.function());
     ASSERT(!function.IsNull());
     // Since the code is referenced from the frame and the ZoneHandle,
@@ -1358,7 +1359,13 @@ DEFINE_RUNTIME_ENTRY(StackOverflow, 0) {
     ASSERT(function.unoptimized_code() != Object::null());
     intptr_t osr_id =
         Code::Handle(function.unoptimized_code()).GetDeoptIdForOsr(frame->pc());
-    ASSERT(osr_id != Compiler::kNoOSRDeoptId);
+    if (osr_id == Compiler::kNoOSRDeoptId) {
+      // The unoptimized code can have been reset to the lazy-compile stub

[rmacnak, 2016/07/06 17:31:57]

As discussed offline, this should be

if (frame.code != frame.code.function.unoptimizedcode) {
  bailout, the frame's code is old, probably from before a reload.
  compiling osr may result in code with different deopt ids.
}

+      // by an isolate reload. We can't do OSR in this invocation.
+      ASSERT(function.unoptimized_code() ==
+             StubCode::LazyCompile_entry()->code());
+      return;
+    }
     if (FLAG_trace_osr) {
       OS::Print("Attempting OSR for %s at id=%" Pd ", count=%" Pd "\n",
                 function.ToFullyQualifiedCString(),