Reland "Leak reports collect information about the last uptrend"

components/metrics/leak_detector/call_stack_table.h

Index: components/metrics/leak_detector/call_stack_table.h
diff --git a/components/metrics/leak_detector/call_stack_table.h b/components/metrics/leak_detector/call_stack_table.h
index 77a4b2a3ed717d882f44fb2403eb93b73315348d..83727167c5cd860ab5250e55cb00059a6d0cef50 100644
--- a/components/metrics/leak_detector/call_stack_table.h
+++ b/components/metrics/leak_detector/call_stack_table.h
@@ -48,6 +48,21 @@ class CallStackTable {
   // must already be initialized with that number.
   void GetTopCallStacks(RankedSet* top_entries) const;
 
+  // Updates information about the last seen drop in the number of allocations
+  // and sets the |previous_count| for every stored call stack, both inside
+  // |entry_map_|. It should be called in the analysis phase, before the
+  // reports are generated, with |timestamp| describing current point in the
+  // timeline.
+  void UpdateLastDropInfo(size_t timestamp);
+
+  // Retrieves the change in timestamp and allocation count since the last
+  // observed drop in the number for allocations for the given call stack
+  // (or since the oldest kept record for the call stacks if there were no
+  // drops)
+  void GetLastUptrendInfo(
+      const CallStack* call_stack, size_t timestamp, size_t *timestamp_delta,
+      uint32_t *count_delta) const;
+
   const LeakAnalyzer& leak_analyzer() const { return leak_analyzer_; }
 
   size_t size() const { return entry_map_.size(); }
@@ -57,6 +72,13 @@ class CallStackTable {
   uint32_t num_frees() const { return num_frees_; }
 
  private:
+  struct CallStackCountInfo {
+    uint32_t count, previous_count, last_drop_count;
+    size_t last_drop_timestamp;
+    CallStackCountInfo() : count(0), previous_count(0), last_drop_count(0),
+                           last_drop_timestamp(0) {}
+  };
+
   // Total number of allocs and frees in this table.
   uint32_t num_allocs_;
   uint32_t num_frees_;
@@ -64,13 +86,13 @@ class CallStackTable {
   // Hash table containing entries. Uses CustomAllocator to avoid recursive
   // malloc hook invocation when analyzing allocs and frees.
   using TableEntryAllocator =
-      STLAllocator<std::pair<const CallStack* const, uint32_t>,
+      STLAllocator<std::pair<const CallStack* const, CallStackCountInfo>,
                    CustomAllocator>;
 
   // Stores a mapping of each call stack to the number of recorded allocations
   // made from that call site.
   base::hash_map<const CallStack*,
-                 uint32_t,
+                 CallStackCountInfo,
                  StoredHash,
                  std::equal_to<const CallStack*>,
                  TableEntryAllocator> entry_map_;