[tracing] Turn StackFrame into struct.

base/trace_event/heap_profiler_stack_frame_deduplicator.cc

Index: base/trace_event/heap_profiler_stack_frame_deduplicator.cc
diff --git a/base/trace_event/heap_profiler_stack_frame_deduplicator.cc b/base/trace_event/heap_profiler_stack_frame_deduplicator.cc
index 12121937530ff30503e6c6dd0a5f65cc38f4bedc..22957804f137b38b44f1610e6621c698702bbbd3 100644
--- a/base/trace_event/heap_profiler_stack_frame_deduplicator.cc
+++ b/base/trace_event/heap_profiler_stack_frame_deduplicator.cc
@@ -31,7 +31,7 @@ int StackFrameDeduplicator::Insert(const StackFrame* beginFrame,
   std::map<StackFrame, int>* nodes = &roots_;
 
   // Loop through the frames, early out when a frame is null.
-  for (const StackFrame* it = beginFrame; it != endFrame && *it; it++) {
+  for (const StackFrame* it = beginFrame; it != endFrame; it++) {
     StackFrame frame = *it;
 
     auto node = nodes->find(frame);
@@ -78,7 +78,19 @@ void StackFrameDeduplicator::AppendAsTraceFormat(std::string* out) const {
     out->append(stringify_buffer);
 
     std::unique_ptr<TracedValue> frame_node_value(new TracedValue);
-    frame_node_value->SetString("name", frame_node->frame);
+    const StackFrame& frame = frame_node->frame;
+    switch (frame.type) {
+      case StackFrame::Type::TRACE_EVENT_NAME:
+        frame_node_value->SetString(
+            "name", static_cast<const char*>(frame.value));
+        break;
+      case StackFrame::Type::THREAD_NAME:
+        SStringPrintf(&stringify_buffer,
+                      "[Thread: %s]",
+                      static_cast<const char*>(frame.value));
+        frame_node_value->SetString("name", stringify_buffer);
+        break;

[Primiano Tucci (use gerrit), 2016/04/19 19:45:06]

maybe add a default: NOTREACHED() (not 100% sure that won't cause a compiler
error though, try)

[Dmitry Skiba, 2016/04/19 22:14:14]

Actually, since we're switching on enum (enum class even) value, compiler issues
a warning, which is treated as error, if not all values are handled:

../../base/trace_event/heap_profiler_stack_frame_deduplicator.cc:82:13: error:
enumeration value 'BLA' not handled in switch [-Werror,-Wswitch]
    switch (frame.type) {

adding 'default: NOTREACHED()' suppresses that, i.e. converts compile time error
into runtime error. Latest thread about that on chromium-dev:
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/A1NV70Hx980

[Primiano Tucci (use gerrit), 2016/04/20 13:17:59]

Sg, leave it as it is then. 

+    }
     if (frame_node->parent_frame_index >= 0) {
       SStringPrintf(&stringify_buffer, "%d", frame_node->parent_frame_index);
       frame_node_value->SetString("parent", stringify_buffer);