zero-copy: Clarify to allocate/destroy GpuMemoryBuffer on any thread and use it on the main thread o

content/common/gpu/gpu_memory_buffer_factory_io_surface.cc

Index: content/common/gpu/gpu_memory_buffer_factory_io_surface.cc
diff --git a/content/common/gpu/gpu_memory_buffer_factory_io_surface.cc b/content/common/gpu/gpu_memory_buffer_factory_io_surface.cc
index 604c1b4927388f956c415939b023ce24b242932c..b6135497b5a56bf168efe1bbfd1ecf7628bcb314 100644
--- a/content/common/gpu/gpu_memory_buffer_factory_io_surface.cc
+++ b/content/common/gpu/gpu_memory_buffer_factory_io_surface.cc
@@ -104,6 +104,7 @@ GpuMemoryBufferFactoryIOSurface::CreateGpuMemoryBuffer(
     gfx::GpuMemoryBuffer::Usage usage,
     int client_id,
     gfx::PluginWindowHandle surface_handle) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   base::ScopedCFTypeRef<CFMutableDictionaryRef> properties;
   properties.reset(CFDictionaryCreateMutable(kCFAllocatorDefault,
                                              0,
@@ -121,13 +122,9 @@ GpuMemoryBufferFactoryIOSurface::CreateGpuMemoryBuffer(
   if (!io_surface)
     return gfx::GpuMemoryBufferHandle();
 
-  {
-    base::AutoLock lock(io_surfaces_lock_);
-
-    IOSurfaceMapKey key(id, client_id);
-    DCHECK(io_surfaces_.find(key) == io_surfaces_.end());
-    io_surfaces_[key] = io_surface;
-  }
+  IOSurfaceMapKey key(id, client_id);
+  DCHECK(io_surfaces_.find(key) == io_surfaces_.end());
+  io_surfaces_[key] = io_surface;
 
   gfx::GpuMemoryBufferHandle handle;
   handle.type = gfx::IO_SURFACE_BUFFER;
@@ -139,8 +136,7 @@ GpuMemoryBufferFactoryIOSurface::CreateGpuMemoryBuffer(
 void GpuMemoryBufferFactoryIOSurface::DestroyGpuMemoryBuffer(
     gfx::GpuMemoryBufferId id,
     int client_id) {
-  base::AutoLock lock(io_surfaces_lock_);
-
+  DCHECK(thread_checker_.CalledOnValidThread());
   IOSurfaceMapKey key(id, client_id);
   IOSurfaceMap::iterator it = io_surfaces_.find(key);
   if (it != io_surfaces_.end())
@@ -158,8 +154,7 @@ GpuMemoryBufferFactoryIOSurface::CreateImageForGpuMemoryBuffer(
     gfx::GpuMemoryBuffer::Format format,
     unsigned internalformat,
     int client_id) {
-  base::AutoLock lock(io_surfaces_lock_);
-
+  DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK_EQ(handle.type, gfx::IO_SURFACE_BUFFER);
   IOSurfaceMapKey key(handle.id, client_id);
   IOSurfaceMap::iterator it = io_surfaces_.find(key);