content: Fix OOM error handling in...

content: Fix OOM error handling in GpuMemoryBufferImplSharedMemory::AllocateSharedMemoryForChildProcess.

We need to run the callback with an empty handle after failing
to allocated shared memory.

BUG=
TBR=piman@chromium.org

Review URL: https://codereview.chromium.org/595063004

Cr-Commit-Position: refs/heads/master@{#296333}

content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc

@@ -43,13 +43,13 @@ void GpuMemoryBufferImplSharedMemory::AllocateSharedMemoryForChildProcess(
     base::ProcessHandle child_process,
     const AllocationCallback& callback) {
   DCHECK(IsLayoutSupported(size, internalformat));
-  gfx::GpuMemoryBufferHandle handle;
   base::SharedMemory shared_memory;
   if (!shared_memory.CreateAnonymous(size.GetArea() *
                                      BytesPerPixel(internalformat))) {
-    handle.type = gfx::EMPTY_BUFFER;
+    callback.Run(gfx::GpuMemoryBufferHandle());
     return;
   }
+  gfx::GpuMemoryBufferHandle handle;
   handle.type = gfx::SHARED_MEMORY_BUFFER;
   shared_memory.GiveToProcess(child_process, &handle.handle);
   callback.Run(handle);