gpu: Disallow zero sized offscreen framebuffers

content/common/gpu/gpu_command_buffer_stub.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/hash.h"
 #include "base/json/json_writer.h"
 #include "base/memory/shared_memory.h"
@@ skipping 183 matching lines @@
         new GpuCommandBufferMemoryTracker(channel),
         channel_->gpu_channel_manager()->shader_translator_cache(),
         NULL,
         subscription_ref_set,
         pending_valuebuffer_state,
         attrib_parser.bind_generates_resource);
   }
 
   use_virtualized_gl_context_ |=
       context_group_->feature_info()->workarounds().use_virtualized_gl_contexts;
+
+  bool is_offscreen = surface_id_ == 0;
+  if (is_offscreen && initial_size_.IsEmpty()) {

[hendrikw, 2015/04/24 18:33:38]

I might rename initial_size_ to initial_offscreen_size_ later, it's a bit
misleading as it.

+    // If we're an offscreen surface with zero width and/or height, set to a
+    // non-zero size so that we have a complete framebuffer for operations like
+    // glClear.
+    initial_size_ = gfx::Size(1, 1);
+  }
 }
 
 GpuCommandBufferStub::~GpuCommandBufferStub() {
   Destroy();
 
   GpuChannelManager* gpu_channel_manager = channel_->gpu_channel_manager();
   gpu_channel_manager->Send(new GpuHostMsg_DestroyCommandBuffer(surface_id()));
 }
 
 GpuMemoryManager* GpuCommandBufferStub::GetMemoryManager() const {
@@ skipping 888 matching lines @@
   Send(new GpuCommandBufferMsg_SwapBuffersCompleted(route_id_, latency_info));
 }
 
 void GpuCommandBufferStub::SendUpdateVSyncParameters(base::TimeTicks timebase,
                                                      base::TimeDelta interval) {
   Send(new GpuCommandBufferMsg_UpdateVSyncParameters(route_id_, timebase,
                                                      interval));
 }
 
 }  // namespace content