Avoid double-counting in GpuChannel memory tracking.

GpuChannel currently calculates current memory usage by iterating over
all stubs and summing their individual memory usage. This results in
double counting as a given stub may share its memory tracker with other
stubs, if they are in a share group.

To avoid double counting, we now iterate over stubs to collect a set of
unique MemoryTrackers, then sum the memory usage of each unique tracker.

BUG=512535

Review URL: https://codereview.chromium.org/1244843004

Cr-Commit-Position: refs/heads/master@{#339746}

content/common/gpu/gpu_channel.cc

@@ -844,11 +844,20 @@ void GpuChannel::RemoveFilter(IPC::MessageFilter* filter) {
 }
 
 uint64 GpuChannel::GetMemoryUsage() {
-  uint64 size = 0;
+  // Collect the unique memory trackers in use by the |stubs_|.
+  std::set<gpu::gles2::MemoryTracker*> unique_memory_trackers;
   for (StubMap::Iterator<GpuCommandBufferStub> it(&stubs_);
        !it.IsAtEnd(); it.Advance()) {
-    size += it.GetCurrentValue()->GetMemoryUsage();
+    unique_memory_trackers.insert(it.GetCurrentValue()->GetMemoryTracker());
   }
+
+  // Sum the memory usage for all unique memory trackers.
+  uint64 size = 0;
+  for (auto* tracker : unique_memory_trackers) {
+    size += gpu_channel_manager()->gpu_memory_manager()->GetTrackerMemoryUsage(
+        tracker);
+  }
+
   return size;
 }
 

content/common/gpu/gpu_command_buffer_stub.cc

@@ -1149,10 +1149,6 @@ void GpuCommandBufferStub::MarkContextLost() {
   command_buffer_->SetParseError(gpu::error::kLostContext);
 }
 
-uint64 GpuCommandBufferStub::GetMemoryUsage() const {
-  return GetMemoryManager()->GetClientMemoryUsage(this);
-}
-
 void GpuCommandBufferStub::SendSwapBuffersCompleted(
     const std::vector<ui::LatencyInfo>& latency_info,
     gfx::SwapResult result) {

content/common/gpu/gpu_command_buffer_stub.h

@@ -148,8 +148,6 @@ class GpuCommandBufferStub
 
   const gpu::gles2::FeatureInfo* GetFeatureInfo() const;
 
-  uint64 GetMemoryUsage() const;
-
   void SendSwapBuffersCompleted(
       const std::vector<ui::LatencyInfo>& latency_info,
       gfx::SwapResult result);

content/common/gpu/gpu_memory_manager.cc

@@ -206,10 +206,10 @@ void GpuMemoryManager::SetClientStateVisible(
   ScheduleManage(visible ? kScheduleManageNow : kScheduleManageLater);
 }
 
-uint64 GpuMemoryManager::GetClientMemoryUsage(
-    const GpuMemoryManagerClient* client) const {
+uint64 GpuMemoryManager::GetTrackerMemoryUsage(
+    gpu::gles2::MemoryTracker* tracker) const {
   TrackingGroupMap::const_iterator tracking_group_it =
-      tracking_groups_.find(client->GetMemoryTracker());
+      tracking_groups_.find(tracker);
   DCHECK(tracking_group_it != tracking_groups_.end());
   return tracking_group_it->second->GetSize();
 }

content/common/gpu/gpu_memory_manager.h

@@ -62,7 +62,7 @@ class CONTENT_EXPORT GpuMemoryManager :
   GpuMemoryTrackingGroup* CreateTrackingGroup(
       base::ProcessId pid, gpu::gles2::MemoryTracker* memory_tracker);
 
-  uint64 GetClientMemoryUsage(const GpuMemoryManagerClient* client) const;
+  uint64 GetTrackerMemoryUsage(gpu::gles2::MemoryTracker* tracker) const;
   uint64 GetMaximumClientAllocation() const {
     return client_hard_limit_bytes_;
   }