components: Add out-of-line copy ctors for complex classes.

components/metrics/leak_detector/leak_detector_impl.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_IMPL_H_
 #define COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 21 matching lines @@
   // allocs and frees.
   template <typename T>
   using InternalList = std::list<T, STLAllocator<T, CustomAllocator>>;
   template <typename T>
   using InternalVector = std::vector<T, STLAllocator<T, CustomAllocator>>;
 
   // Leak report generated by LeakDetectorImpl.
   class LeakReport {
    public:
     LeakReport();
+    LeakReport(const LeakReport& other);
     ~LeakReport();
 
     size_t alloc_size_bytes() const { return alloc_size_bytes_; }
 
     const InternalVector<uintptr_t>& call_stack() const { return call_stack_; }
 
     const InternalVector<InternalVector<uint32_t>>& size_breakdown_history()
         const {
       return size_breakdown_history_;
     }
@@ skipping 123 matching lines @@
   // considered a leak suspect.
   int call_stack_suspicion_threshold_;
 
   DISALLOW_COPY_AND_ASSIGN(LeakDetectorImpl);
 };
 
 }  // namespace leak_detector
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_IMPL_H_