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

runtime/vm/profiler.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 "platform/address_sanitizer.h"
 #include "platform/memory_sanitizer.h"
 #include "platform/utils.h"
 
 #include "vm/allocation.h"
 #include "vm/atomic.h"
@@ skipping 60 matching lines @@
   Sample::InitOnce();
   if (!FLAG_profiler) {
     return;
   }
   ASSERT(!initialized_);
   sample_buffer_ = new SampleBuffer();
   Profiler::InitAllocationSampleBuffer();
   // Zero counters.
   memset(&counters_, 0, sizeof(counters_));
   NativeSymbolResolver::InitOnce();
+  ThreadInterrupter::InitOnce();
   ThreadInterrupter::SetInterruptPeriod(FLAG_profile_period);
   ThreadInterrupter::Startup();
   initialized_ = true;
 }
 
 void Profiler::InitAllocationSampleBuffer() {
   if (FLAG_profiler_native_memory &&
       (Profiler::allocation_sample_buffer_ == NULL)) {
     Profiler::allocation_sample_buffer_ = new AllocationSampleBuffer();
   }
 }
 
 void Profiler::Shutdown() {
   if (!FLAG_profiler) {
     return;
   }
   ASSERT(initialized_);
   ThreadInterrupter::Shutdown();
   NativeSymbolResolver::ShutdownOnce();
+#if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) || defined(HOST_OS_ANDROID)
+  // TODO(30309): Free the sample buffer on platforms that use a signal-based
+  // thread interrupter.
+#else
+  delete sample_buffer_;
+  sample_buffer_ = NULL;
+#endif
 }
 
 void Profiler::SetSampleDepth(intptr_t depth) {
   const int kMinimumDepth = 2;
   const int kMaximumDepth = 255;
   if (depth < kMinimumDepth) {
     FLAG_max_profile_depth = kMinimumDepth;
   } else if (depth > kMaximumDepth) {
     FLAG_max_profile_depth = kMaximumDepth;
   } else {
@@ skipping 1571 matching lines @@
 }
 
 ProcessedSampleBuffer::ProcessedSampleBuffer()
     : code_lookup_table_(new CodeLookupTable(Thread::Current())) {
   ASSERT(code_lookup_table_ != NULL);
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart