[vm] Don't disregard KernelLoader::LoadProgram result when bootstrapping

It might be an error, in which case Isolate is left in half initialized
state.

Change-Id: I011ce2b4bbbe5a84f6579eb6d4d22ea5c1afbd3a
Reviewed-on: https://dart-review.googlesource.com/27801
Reviewed-by: Alexander Markov <[email protected]>
Commit-Queue: Vyacheslav Egorov <[email protected]>

runtime/vm/bootstrap.cc

@@ -334,7 +334,10 @@ static RawError* BootstrapFromKernel(Thread* thread, kernel::Program* program) {
 
   // The platform binary may contain other libraries (e.g., dart:_builtin or
   // dart:io) that will not be bundled with application.  Load them now.
-  loader.LoadProgram();
+  const Object& result = loader.LoadProgram();
+  if (result.IsError()) {
+    return Error::Cast(result).raw();
+  }
 
   // The builtin library should be registered with the VM.
   dart_name = String::New("dart:_builtin");

runtime/vm/bootstrap_nocore.cc

@@ -94,7 +94,10 @@ RawError* BootstrapFromKernel(Thread* thread, kernel::Program* program) {
 
   // The platform binary may contain other libraries (e.g., dart:_builtin or
   // dart:io) that will not be bundled with application.  Load them now.
-  loader.LoadProgram();
+  const Object& result = loader.LoadProgram();
+  if (result.IsError()) {
+    return Error::Cast(result).raw();
+  }
 
   // The builtin library should be registered with the VM.
   dart_name = String::New("dart:_builtin");