Make cc:RenderingStats a move-only type.

It contains six std::vector<> members, so the implicit copy in TakeImplThreadRenderingStats() may end up doing six memory allocations
while holding a lock.

Change-Id: I46b20c83679b44a334a8905fd6e76204bf3e2854
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5982361
Reviewed-by: Khushal Sagar <khushalsagar@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1376659}

cc/debug/rendering_stats.cc

@@ -10,8 +10,10 @@ namespace cc {
 
 RenderingStats::TimeDeltaList::TimeDeltaList() = default;
 
-RenderingStats::TimeDeltaList::TimeDeltaList(const TimeDeltaList& other) =
+RenderingStats::TimeDeltaList::TimeDeltaList(TimeDeltaList&& other) = default;
-    default;
+
+RenderingStats::TimeDeltaList& RenderingStats::TimeDeltaList::operator=(
+    TimeDeltaList&& other) = default;
 
 RenderingStats::TimeDeltaList::~TimeDeltaList() = default;
 
@@ -39,7 +41,9 @@ base::TimeDelta RenderingStats::TimeDeltaList::GetLastTimeDelta() const {
 
 RenderingStats::RenderingStats() = default;
 
-RenderingStats::RenderingStats(const RenderingStats& other) = default;
+RenderingStats::RenderingStats(RenderingStats&& other) = default;
+
+RenderingStats& RenderingStats::operator=(RenderingStats&& other) = default;
 
 RenderingStats::~RenderingStats() = default;
 

cc/debug/rendering_stats.h

@@ -21,7 +21,10 @@ struct CC_DEBUG_EXPORT RenderingStats {
   class CC_DEBUG_EXPORT TimeDeltaList {
    public:
     TimeDeltaList();
-    TimeDeltaList(const TimeDeltaList& other);
+    TimeDeltaList(const TimeDeltaList& other) = delete;
+    TimeDeltaList(TimeDeltaList&& other);
+    TimeDeltaList& operator=(const TimeDeltaList& other) = delete;
+    TimeDeltaList& operator=(TimeDeltaList&& other);
     ~TimeDeltaList();
 
     void Append(base::TimeDelta value);
@@ -37,7 +40,10 @@ struct CC_DEBUG_EXPORT RenderingStats {
   };
 
   RenderingStats();
-  RenderingStats(const RenderingStats& other);
+  RenderingStats(const RenderingStats& other) = delete;
+  RenderingStats(RenderingStats&& other);
+  RenderingStats& operator=(const RenderingStats& other) = delete;
+  RenderingStats& operator=(RenderingStats&& other);
   ~RenderingStats();
 
   int64_t frame_count = 0;

cc/debug/rendering_stats_instrumentation.cc

@@ -6,6 +6,8 @@
 
 #include <stdint.h>
 
+#include <utility>
+
 #include "base/memory/ptr_util.h"
 
 namespace cc {
@@ -24,7 +26,7 @@ RenderingStatsInstrumentation::~RenderingStatsInstrumentation() = default;
 
 RenderingStats RenderingStatsInstrumentation::TakeImplThreadRenderingStats() {
   base::AutoLock scoped_lock(lock_);
-  auto stats = impl_thread_rendering_stats_;
+  auto stats = std::move(impl_thread_rendering_stats_);
   impl_thread_rendering_stats_ = RenderingStats();
   return stats;
 }