Leak reports collect information about the last uptrend

components/metrics/leak_detector/call_stack_table.cc

Index: components/metrics/leak_detector/call_stack_table.cc
diff --git a/components/metrics/leak_detector/call_stack_table.cc b/components/metrics/leak_detector/call_stack_table.cc
index 8f9540bc0d4b35f6f619c350fd8c13ba2fc1514f..ec9b78699ce635bf95eb2e1c712e688bd1f395b8 100644
--- a/components/metrics/leak_detector/call_stack_table.cc
+++ b/components/metrics/leak_detector/call_stack_table.cc
@@ -42,7 +42,7 @@ CallStackTable::CallStackTable(int call_stack_suspicion_threshold)
 CallStackTable::~CallStackTable() {}
 
 void CallStackTable::Add(const CallStack* call_stack) {
-  ++entry_map_[call_stack];
+  ++entry_map_[call_stack].count;
   ++num_allocs_;
 }
 
@@ -50,7 +50,7 @@ void CallStackTable::Remove(const CallStack* call_stack) {
   auto iter = entry_map_.find(call_stack);
   if (iter == entry_map_.end())
     return;
-  uint32_t& count_for_call_stack = iter->second;
+  uint32_t& count_for_call_stack = iter->second.count;
   --count_for_call_stack;
   ++num_frees_;
 
@@ -67,9 +67,40 @@ void CallStackTable::TestForLeaks() {
 }
 
 void CallStackTable::GetTopCallStacks(RankedSet* top_entries) const {
-  for (const auto& call_stack_and_count : entry_map_) {
-    top_entries->AddCallStack(call_stack_and_count.first,
-                              call_stack_and_count.second);
+  for (const auto& call_stack_count_info : entry_map_) {
+    top_entries->AddCallStack(call_stack_count_info.first,
+                              call_stack_count_info.second.count);
+  }
+}
+
+void CallStackTable::UpdateLastDropInfo(size_t timestamp) {
+  for (auto& call_stack_and_info : entry_map_) {
+    auto& count_info = call_stack_and_info.second;
+
+    // If the |previous_count| is 0 then we need to initialize info.
+    if (count_info.previous_count == 0 ||
+        count_info.count < count_info.previous_count) {
+      count_info.last_drop_timestamp = timestamp;
+      count_info.last_drop_count = count_info.count;
+    }
+    count_info.previous_count = count_info.count;
+  }
+}
+
+void CallStackTable::GetLastUptrendInfo(
+    const CallStack* call_stack, size_t timestamp, size_t* timestamp_delta,
+    uint32_t* count_delta) const {
+  const auto& call_stack_count_info_iter = entry_map_.find(call_stack);
+
+  if (call_stack_count_info_iter != entry_map_.end()) {
+    const auto& count_info = call_stack_count_info_iter->second;
+    *timestamp_delta = timestamp - count_info.last_drop_timestamp;
+    *count_delta = count_info.count - count_info.last_drop_count;
+  } else {
+    DLOG(WARNING) << "Accessing information about a call stack that has not "
+                  << "been recorded";
+    *timestamp_delta = timestamp;
+    *count_delta = 0;
   }
 }