[tracing] Turn StackFrame into struct.

base/trace_event/heap_profiler_allocation_context.cc

Index: base/trace_event/heap_profiler_allocation_context.cc
diff --git a/base/trace_event/heap_profiler_allocation_context.cc b/base/trace_event/heap_profiler_allocation_context.cc
index 038c083f0fa83241f9fef46c0ed239572d282d62..aacc7b048d00ad9f8d2b3cf9a2c437c7dfd1c466 100644
--- a/base/trace_event/heap_profiler_allocation_context.cc
+++ b/base/trace_event/heap_profiler_allocation_context.cc
@@ -12,27 +12,27 @@
 namespace base {
 namespace trace_event {
 
-// Constructor that does not initialize members.
-AllocationContext::AllocationContext() {}
-
-// static
-AllocationContext AllocationContext::Empty() {
-  AllocationContext ctx;
-
-  for (size_t i = 0; i < arraysize(ctx.backtrace.frames); i++)
-    ctx.backtrace.frames[i] = nullptr;
+bool operator < (const StackFrame& lhs, const StackFrame& rhs) {
+  return lhs.value < rhs.value;
+}
 
-  ctx.type_name = nullptr;
+bool operator == (const StackFrame& lhs, const StackFrame& rhs) {
+  return lhs.value == rhs.value;
+}
 
-  return ctx;
+bool operator != (const StackFrame& lhs, const StackFrame& rhs) {
+  return !(lhs.value == rhs.value);
 }
 
+Backtrace::Backtrace(): frame_count(0) {}
+
 bool operator==(const Backtrace& lhs, const Backtrace& rhs) {
-  // Pointer equality of the stack frames is assumed, so instead of doing a deep
-  // string comparison on all of the frames, a |memcmp| suffices.
-  return std::memcmp(lhs.frames, rhs.frames, sizeof(lhs.frames)) == 0;
+  if (lhs.frame_count != rhs.frame_count) return false;
+  return std::equal(lhs.frames, lhs.frames + lhs.frame_count, rhs.frames);
 }
 
+AllocationContext::AllocationContext(): type_name(nullptr) {}
+
 bool operator==(const AllocationContext& lhs, const AllocationContext& rhs) {
   return (lhs.backtrace == rhs.backtrace) && (lhs.type_name == rhs.type_name);
 }
@@ -43,10 +43,19 @@ bool operator==(const AllocationContext& lhs, const AllocationContext& rhs) {
 namespace BASE_HASH_NAMESPACE {
 using base::trace_event::AllocationContext;
 using base::trace_event::Backtrace;
+using base::trace_event::StackFrame;
+
+size_t hash<StackFrame>::operator()(const StackFrame& frame) const {
+  return hash<const void*>()(frame.value);
+}
 
 size_t hash<Backtrace>::operator()(const Backtrace& backtrace) const {
-  return base::SuperFastHash(reinterpret_cast<const char*>(backtrace.frames),
-                             sizeof(backtrace.frames));
+  const void* values[Backtrace::kMaxFrameCount];
+  for (size_t i = 0; i != backtrace.frame_count; ++i) {
+    values[i] = backtrace.frames[i].value;
+  }
+  return base::SuperFastHash(reinterpret_cast<const char*>(values),
+                             backtrace.frame_count * sizeof(*values));
 }
 
 size_t hash<AllocationContext>::operator()(const AllocationContext& ctx) const {