Add reference-counting for mailbox textures.

content/common/gpu/gpu_command_buffer_stub.cc

Index: content/common/gpu/gpu_command_buffer_stub.cc
diff --git a/content/common/gpu/gpu_command_buffer_stub.cc b/content/common/gpu/gpu_command_buffer_stub.cc
index 04e55bcbab539f3e76bc8b413f1dac5c05381738..bf62a1e6d503b38f27dd58d7456585b1eb4b7acc 100644
--- a/content/common/gpu/gpu_command_buffer_stub.cc
+++ b/content/common/gpu/gpu_command_buffer_stub.cc
@@ -25,6 +25,7 @@
 #include "gpu/command_buffer/common/constants.h"
 #include "gpu/command_buffer/common/gles2_cmd_utils.h"
 #include "gpu/command_buffer/service/gl_context_virtual.h"
+#include "gpu/command_buffer/service/mailbox_manager.h"
 #include "gpu/command_buffer/service/memory_tracking.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_switches.h"
@@ -940,4 +941,14 @@ void GpuCommandBufferStub::SetMemoryAllocation(
   last_memory_allocation_ = allocation;
 }
 
+void GpuCommandBufferStub::OnDestroySurface(int surface_id) {
+  gpu::gles2::MailboxManager* manager = context_group_->mailbox_manager();
+  if (manager) {
+    manager->RemoveTexturesFromPool(
+        std::make_pair(gpu::gles2::MailboxManager::TEXTURE_POOL_FOR_SURFACE,
+                       surface_id),
+        MakeCurrent());
+  }
+}
+
 }  // namespace content