Fix clearing compile time constant caches during tree shaking.

runtime/vm/precompiler.cc

Index: runtime/vm/precompiler.cc
diff --git a/runtime/vm/precompiler.cc b/runtime/vm/precompiler.cc
index 4ba710b69aeb6b8892a0e4132c2c1da5466e6b07..13c4595e5535617f29b3711ded14422758982ca5 100644
--- a/runtime/vm/precompiler.cc
+++ b/runtime/vm/precompiler.cc
@@ -241,6 +241,7 @@ void Precompiler::DoCompileAll(
 
       // Clear these before dropping classes as they may hold onto otherwise
       // dead instances of classes we will remove.
+      DropCompileTimeConstantCaches();
       I->object_store()->set_unique_dynamic_targets(Array::null_array());
       Class& null_class = Class::Handle(Z);
       I->object_store()->set_future_class(null_class);
@@ -1559,6 +1560,21 @@ void Precompiler::DropTypeArguments() {
 }
 
 
+void Precompiler::DropCompileTimeConstantCaches() {
+  Library& lib = Library::Handle(Z);
+  Array& scripts = Array::Handle(Z);
+  Script& script = Script::Handle(Z);
+  for (intptr_t i = 0; i < libraries_.Length(); i++) {
+    lib ^= libraries_.At(i);
+    scripts = lib.LoadedScripts();
+    for (intptr_t j = 0; j < scripts.Length(); j++) {
+      script ^= scripts.At(j);
+      script.set_compile_time_constants(Array::null_array());
+    }
+  }
+}
+
+
 void Precompiler::TraceTypesFromRetainedClasses() {
   Library& lib = Library::Handle(Z);
   Class& cls = Class::Handle(Z);