Only reload libraries when they may have been modified.

runtime/vm/code_generator.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/code_generator.h"
 
 #include "vm/assembler.h"
 #include "vm/ast.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
@@ skipping 1342 matching lines @@
   }
   if (do_deopt) {
     // TODO(turnidge): Consider using DeoptimizeAt instead.
     DeoptimizeFunctionsOnStack();
   }
   if (do_reload) {
 #ifndef PRODUCT
     // Maybe adjust the rate of future reloads.
     isolate->MaybeIncreaseReloadEveryNStackOverflowChecks();
     // Issue a reload.
-    isolate->ReloadSources();
+    isolate->ReloadSources(true /* force_reload */);
     const Error& error = Error::Handle(isolate->sticky_reload_error());
     if (!error.IsNull()) {
       FATAL1("*** Isolate reload failed: %s\n", error.ToErrorCString());
     }
 #endif
   }
   if (FLAG_support_debugger && do_stacktrace) {
     String& var_name = String::Handle();
     Instance& var_value = Instance::Handle();
     // Collecting the stack trace and accessing local variables
@@ skipping 585 matching lines @@
   const intptr_t elm_size = old_data.ElementSizeInBytes();
   const TypedData& new_data =
       TypedData::Handle(TypedData::New(cid, new_size, Heap::kOld));
   TypedData::Copy(new_data, 0, old_data, 0, old_size * elm_size);
   typed_data_cell.SetAt(0, new_data);
   arguments.SetReturn(new_data);
 }
 
 
 }  // namespace dart