[NFC][sanitizer] Add a few consts

[vitalybuka]

Summary

Depends on D111609.

[vitalybuka]

rebase

compiler-rt/lib/sanitizer_common/sanitizer_stackdepot.h

 namespace __sanitizer {
 
 // StackDepot efficiently stores huge amounts of stack traces.
 struct StackDepotNode;
 struct StackDepotHandle {
   StackDepotNode *node_;
   StackDepotHandle() : node_(nullptr) {}
   explicit StackDepotHandle(StackDepotNode *node) : node_(node) {}
-  bool valid() { return node_; }
-  u32 id();
-  int use_count();
+  bool valid() const { return node_; }
+  u32 id() const;
+  int use_count() const;
   void inc_use_count_unsafe();
 };
 
 const int kStackDepotMaxUseCount = 1U << (SANITIZER_ANDROID ? 16 : 20);
 
 StackDepotStats StackDepotGetStats();
 u32 StackDepotPut(StackTrace stack);
 StackDepotHandle StackDepotPut_WithHandle(StackTrace stack);

compiler-rt/lib/sanitizer_common/sanitizer_stackdepot.cpp

struct StackDepotNode {
   }
   StackDepotHandle get_handle() { return StackDepotHandle(this); }
 
   typedef StackDepotHandle handle_type;
 };
 
 COMPILER_CHECK(StackDepotNode::kMaxUseCount >= (u32)kStackDepotMaxUseCount);
 
-u32 StackDepotHandle::id() { return node_->id; }
-int StackDepotHandle::use_count() {
+u32 StackDepotHandle::id() const { return node_->id; }
+int StackDepotHandle::use_count() const {
   return atomic_load(&node_->tag_and_use_count, memory_order_relaxed) &
          StackDepotNode::kUseCountMask;
 }
 void StackDepotHandle::inc_use_count_unsafe() {
   u32 prev =
       atomic_fetch_add(&node_->tag_and_use_count, 1, memory_order_relaxed) &
       StackDepotNode::kUseCountMask;
   CHECK_LT(prev + 1, StackDepotNode::kMaxUseCount);