Factor cpu profile tree into separate element and expose allocation tracing UI

runtime/vm/profiler_service.cc

 // Copyright (c) 2015, 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/profiler_service.h"
 
 #include "vm/growable_array.h"
 #include "vm/native_symbol.h"
 #include "vm/object.h"
 #include "vm/os.h"
@@ skipping 1220 matching lines @@
 
       // Walk the sampled PCs.
       for (intptr_t j = sample->length() - 1; j >= 0; j--) {
         ASSERT(sample->At(j) != 0);
         current = ProcessFunctionPC(
             sample->At(j),
             sample->timestamp(),
             current,
             i,
             (j == 0),
-            sample->first_frame_executing(),
+            sample->first_frame_executing() || sample->IsAllocationSample(),
             true);
       }
     }
   }
 
   void BuildExclusiveFunctionTrie(ProfileFunctionTrieNode* root) {
     ScopeTimer sw("ProfileBuilder::BuildExclusiveFunctionTrie",
                   FLAG_trace_profiler);
     for (intptr_t i = 0; i < samples_->length(); i++) {
       ProcessedSample* sample = samples_->At(i);
 
       // Tick the root.
       ProfileFunctionTrieNode* current = root;
       current->Tick();
 
       // VM & User tags.
       current = AppendTags(sample->vm_tag(), sample->user_tag(), current);
 
       // Walk the sampled PCs.
       for (intptr_t j = 0; j < sample->length(); j++) {
         ASSERT(sample->At(j) != 0);
         current = ProcessFunctionPC(
             sample->At(j),
             sample->timestamp(),
             current,
             i,
             (j == 0),
-            sample->first_frame_executing(),
+            sample->first_frame_executing() || sample->IsAllocationSample(),
             false);
       }
 
       // Truncated tag.
       if (sample->truncated()) {
         current = AppendTruncatedTag(current);
       }
     }
   }
 
@@ skipping 775 matching lines @@
   ASSERT(sample_buffer != NULL);
 
   ClearProfileVisitor clear_profile(isolate);
   sample_buffer->VisitSamples(&clear_profile);
 
   // Enable profile interrupts.
   Profiler::BeginExecution(isolate);
 }
 
 }  // namespace dart