gpu: Avoid creating two native pixmaps for the same buffer.

gpu/ipc/service/gpu_memory_buffer_factory_ozone_native_pixmap.cc

Index: gpu/ipc/service/gpu_memory_buffer_factory_ozone_native_pixmap.cc
diff --git a/gpu/ipc/service/gpu_memory_buffer_factory_ozone_native_pixmap.cc b/gpu/ipc/service/gpu_memory_buffer_factory_ozone_native_pixmap.cc
index 4d233c6fbf688892c18f1206d8e64f4d099e4b6d..f9630a3cb5f6d9576949f09525657e3afa59aef0 100644
--- a/gpu/ipc/service/gpu_memory_buffer_factory_ozone_native_pixmap.cc
+++ b/gpu/ipc/service/gpu_memory_buffer_factory_ozone_native_pixmap.cc
@@ -75,14 +75,29 @@ GpuMemoryBufferFactoryOzoneNativePixmap::CreateImageForGpuMemoryBuffer(
     int client_id,
     SurfaceHandle surface_handle) {
   DCHECK_EQ(handle.type, gfx::OZONE_NATIVE_PIXMAP);
-  scoped_refptr<ui::NativePixmap> pixmap =
-      ui::OzonePlatform::GetInstance()
-          ->GetSurfaceFactoryOzone()
-          ->CreateNativePixmapFromHandle(surface_handle, size, format,
-                                         handle.native_pixmap_handle);
-  if (!pixmap.get()) {
-    DLOG(ERROR) << "Failed to create pixmap from handle";
-    return nullptr;
+
+  scoped_refptr<ui::NativePixmap> pixmap;
+
+  // If CreateGpuMemoryBuffer was used to allocate this buffer then avoid
+  // creating a new native pixmap for it.
+  {
+    base::AutoLock lock(native_pixmaps_lock_);
+    NativePixmapMapKey key(handle.id.id, client_id);
+    auto it = native_pixmaps_.find(key);
+    if (it != native_pixmaps_.end())
+      pixmap = it->second;
+  }
+
+  // Create new pixmap from handle if one doesn't already exist.
+  if (!pixmap) {
+    pixmap = ui::OzonePlatform::GetInstance()
+                 ->GetSurfaceFactoryOzone()
+                 ->CreateNativePixmapFromHandle(surface_handle, size, format,
+                                                handle.native_pixmap_handle);
+    if (!pixmap.get()) {
+      DLOG(ERROR) << "Failed to create pixmap from handle";
+      return nullptr;
+    }

[piman, 2016/07/27 22:42:14]

Should we add pixmap to the map in this case, so that we reuse it if we call
this again (e.g. for another context/process for any reason)?

[reveman, 2016/07/27 23:13:25]

The client is in control over handle.id in this case and that can cause an issue
if the client uses this to add a pixmap that will cause the DCHECK at line 50 to
fail. It might still be a good idea to do something like what you're suggesting
though or add some GEM handle tracking mechanism at a lower level. I'm going to
land this for now and look at what is the best long term solution as a follow
up.

   }
 
   scoped_refptr<ui::GLImageOzoneNativePixmap> image(