[vm] Don't enable the profiler by default. Enable the profiler at startup with --observe, or later …

runtime/vm/flag_list.h

 // Copyright (c) 2012, 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.
 
 #ifndef RUNTIME_VM_FLAG_LIST_H_
 #define RUNTIME_VM_FLAG_LIST_H_
 
 // Don't use USING_DBC outside of this file.
 #if defined(TARGET_ARCH_DBC)
 #define USING_DBC true
@@ skipping 116 matching lines @@
   P(print_snapshot_sizes, bool, false, "Print sizes of generated snapshots.")  \
   P(print_benchmarking_metrics, bool, false,                                   \
     "Print additional memory and latency metrics for benchmarking.")           \
   R(print_ssa_liveranges, false, bool, false,                                  \
     "Print live ranges after allocation.")                                     \
   R(print_stacktrace_at_api_error, false, bool, false,                         \
     "Attempt to print a native stack trace when an API error is created.")     \
   C(print_stop_message, false, false, bool, false, "Print stop message.")      \
   D(print_variable_descriptors, bool, false,                                   \
     "Print variable descriptors in disassembly.")                              \
-  R(profiler, false, bool, !USING_DBC, "Enable the profiler.")                 \
+  R(profiler, false, bool, false, "Enable the profiler.")                      \
   R(profiler_native_memory, false, bool, false,                                \
     "Enable native memory statistic collection.")                              \
   P(reify_generic_functions, bool, false,                                      \
     "Enable reification of generic functions (not yet supported).")            \
   P(reorder_basic_blocks, bool, true, "Reorder basic blocks")                  \
   P(causal_async_stacks, bool, !USING_PRODUCT, "Improved async stacks")        \
   C(stress_async_stacks, false, false, bool, false,                            \
     "Stress test async stack traces")                                          \
   C(async_debugger, false, false, bool, true,                                  \
     "Debugger support async functions.")                                       \
@@ skipping 26 matching lines @@
   R(verbose_gc_hdr, 40, int, 40, "Print verbose GC header interval.")          \
   R(verify_after_gc, false, bool, false,                                       \
     "Enables heap verification after GC.")                                     \
   R(verify_before_gc, false, bool, false,                                      \
     "Enables heap verification before GC.")                                    \
   D(verify_gc_contains, bool, false,                                           \
     "Enables verification of address contains during GC.")                     \
   D(verify_on_transition, bool, false, "Verify on dart <==> VM.")
 
 #endif  // RUNTIME_VM_FLAG_LIST_H_