Fix edge case where profiler would miss the caller of the top frame

runtime/vm/profiler.h

Index: runtime/vm/profiler.h
diff --git a/runtime/vm/profiler.h b/runtime/vm/profiler.h
index 0b681c41caee8302bc9fcab43f6797b8d60bf41e..98fe57df51e1c3883d599faa5bca59333e5e7fe2 100644
--- a/runtime/vm/profiler.h
+++ b/runtime/vm/profiler.h
@@ -119,8 +119,12 @@ class Sample {
     timestamp_ = timestamp;
     tid_ = tid;
     isolate_ = isolate;
+    pc_marker_ = 0;
     vm_tag_ = VMTag::kInvalidTagId;
     user_tag_ = UserTags::kNoUserTag;
+    sp_ = 0;
+    fp_ = 0;
+    state_ = 0;
     for (intptr_t i = 0; i < kSampleFramesSize; i++) {
       pcs_[i] = 0;
     }
@@ -165,12 +169,66 @@ class Sample {
     user_tag_ = tag;
   }
 
+  uword pc_marker() const {
+    return pc_marker_;
+  }
+
+  void set_pc_marker(uword pc_marker) {
+    pc_marker_ = pc_marker;
+  }
+
+  uword sp() {
+    return sp_;
+  }
+
+  void set_sp(uword sp) {
+    sp_ = sp;
+  }
+
+  uword fp() {
+    return fp_;
+  }
+
+  void set_fp(uword fp) {
+    fp_ = fp;
+  }
+
+  void InsertCallerForTopFrame(uword pc) {
+    // Shift all entries down.
+    for (intptr_t i = 1; i < kSampleFramesSize - 1; i++) {
+      pcs_[i + 1] = pcs_[i];
+    }
+    pcs_[1] = pc;
+  }
+
+  bool processed() const {
+    return ProcessedBit::decode(state_);
+  }
+
+  void set_processed(bool processed) {
+    state_ = ProcessedBit::update(processed, state_);
+  }
+
+  bool leaf_frame_is_dart() const {
+    return LeafFrameIsDart::decode(state_);
+  }
+
+  void set_leaf_frame_is_dart(bool leaf_frame_is_dart) {
+    state_ = LeafFrameIsDart::update(leaf_frame_is_dart, state_);
+  }
+
  private:
+  class ProcessedBit : public BitField<bool, 0, 1> {};
+  class LeafFrameIsDart : public BitField<bool, 1, 1> {};
   int64_t timestamp_;
   ThreadId tid_;
   Isolate* isolate_;
+  uword pc_marker_;
   uword vm_tag_;
   uword user_tag_;
+  uword sp_;
+  uword fp_;
+  uword state_;
   uword pcs_[kSampleFramesSize];
 };
 
@@ -229,6 +287,29 @@ class SampleBuffer {
     }
   }
 
+  void VisitSamplesByReference(SampleVisitor* visitor) {
+    ASSERT(visitor != NULL);
+    Sample* sample;
+    const intptr_t length = capacity();
+    for (intptr_t i = 0; i < length; i++) {
+      sample = At(i);

[srdjan, 2014/05/02 18:20:29]

You can put Sample* sample = At(i); here.
OR
const Sample& sample = *At(i)l

[Cutch, 2014/05/02 18:37:03]

Done.

+      if (sample->isolate() != visitor->isolate()) {
+        // Another isolate.
+        continue;
+      }
+      if (sample->timestamp() == 0) {
+        // Empty.
+        continue;
+      }
+      if (sample->At(0) == 0) {
+        // No frames.
+        continue;
+      }
+      visitor->IncrementVisited();
+      visitor->VisitSample(sample);
+    }
+  }
+
  private:
   Sample* samples_;
   intptr_t capacity_;