Minor cleanups: use GrowableArray::is_empty instead of ::length() == 0

runtime/vm/exceptions.cc

 // Copyright (c) 2011, 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/exceptions.h"
 
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/flags.h"
 #include "vm/object.h"
@@ skipping 125 matching lines @@
   uword handler_fp = 0;
   GrowableArray<uword> stack_frame_pcs;
   bool handler_exists = FindExceptionHandler(&handler_pc,
                                              &handler_sp,
                                              &handler_fp,
                                              &stack_frame_pcs);
   // TODO(5411263): At some point we can optimize by figuring out if a
   // stack trace is needed based on whether the catch code specifies a
   // stack trace object or there is a rethrow in the catch clause.
   Stacktrace& stacktrace = Stacktrace::Handle();
-  if (stack_frame_pcs.length() > 0) {
+  if (!stack_frame_pcs.is_empty()) {
     if (existing_stacktrace.IsNull()) {
       stacktrace = Stacktrace::New(stack_frame_pcs);
     } else {
       stacktrace ^= existing_stacktrace.raw();
       stacktrace.Append(stack_frame_pcs);
     }
   } else {
     stacktrace ^= existing_stacktrace.raw();
   }
   if (FLAG_print_stacktrace_at_throw) {
@@ skipping 260 matching lines @@
     case kIsolateSpawn:
       library = Library::IsolateLibrary();
       class_name = String::NewSymbol("IsolateSpawnException");
       break;
   }
 
   return DartLibraryCalls::ExceptionCreate(library, class_name, arguments);
 }
 
 }  // namespace dart