Add flag to control number of stack frames collected by profiler

runtime/vm/profiler_test.cc

Index: runtime/vm/profiler_test.cc
diff --git a/runtime/vm/profiler_test.cc b/runtime/vm/profiler_test.cc
index b0c580e70eec33eef1e0d3c2df6cd821027966be..1d60853440f5279b5095831c037e77850023f327 100644
--- a/runtime/vm/profiler_test.cc
+++ b/runtime/vm/profiler_test.cc
@@ -17,13 +17,15 @@ class ProfileSampleBufferTestHelper {
   static intptr_t IterateCount(const Isolate* isolate,
                                const SampleBuffer& sample_buffer) {
     intptr_t c = 0;
+    Sample* sample = Sample::Allocate();
     for (intptr_t i = 0; i < sample_buffer.capacity(); i++) {
-      Sample sample = sample_buffer.GetSample(i);
-      if (sample.isolate != isolate) {
+      sample_buffer.CopySample(i, sample);
+      if (sample->isolate != isolate) {
         continue;
       }
       c++;
     }
+    free(sample);
     return c;
   }
 
@@ -31,13 +33,15 @@ class ProfileSampleBufferTestHelper {
   static intptr_t IterateSumPC(const Isolate* isolate,
                                const SampleBuffer& sample_buffer) {
     intptr_t c = 0;
+    Sample* sample = Sample::Allocate();
     for (intptr_t i = 0; i < sample_buffer.capacity(); i++) {
-      Sample sample = sample_buffer.GetSample(i);
-      if (sample.isolate != isolate) {
+      sample_buffer.CopySample(i, sample);
+      if (sample->isolate != isolate) {
         continue;
       }
-      c += sample.pcs[0];
+      c += sample->pcs[0];
     }
+    free(sample);
     return c;
   }
 };